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<h1>underscore.js</h1>
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<pre><code>Underscore.js <span class="hljs-number">1.6</span><span class="hljs-number">.0</span>
http:<span class="hljs-comment">//underscorejs.org</span>
(c) <span class="hljs-number">2009</span>-<span class="hljs-number">2014</span> Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors
Underscore may be freely distributed under the MIT license.
</code></pre>
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<div class="content"><div class='highlight'><pre>
(<span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">()</span> {</span></pre></div></div>
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<h2 id="baseline-setup">Baseline setup</h2>
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<p>Establish the root object, <code>window</code> in the browser, or <code>exports</code> on the server.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">var</span> root = <span class="hljs-keyword">this</span>;</pre></div></div>
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<p>Save the previous value of the <code>_</code> variable.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">var</span> previousUnderscore = root._;</pre></div></div>
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<p>Establish the object that gets returned to break out of a loop iteration.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">var</span> breaker = {};</pre></div></div>
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<p>Save bytes in the minified (but not gzipped) version:</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">var</span> ArrayProto = <span class="hljs-built_in">Array</span>.prototype, ObjProto = <span class="hljs-built_in">Object</span>.prototype, FuncProto = <span class="hljs-built_in">Function</span>.prototype;</pre></div></div>
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<p>Create quick reference variables for speed access to core prototypes.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">var</span>
push = ArrayProto.push,
slice = ArrayProto.slice,
concat = ArrayProto.concat,
toString = ObjProto.toString,
hasOwnProperty = ObjProto.hasOwnProperty;</pre></div></div>
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<p>All <strong>ECMAScript 5</strong> native function implementations that we hope to use
are declared here.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">var</span>
nativeForEach = ArrayProto.forEach,
nativeMap = ArrayProto.map,
nativeReduce = ArrayProto.reduce,
nativeReduceRight = ArrayProto.reduceRight,
nativeFilter = ArrayProto.filter,
nativeEvery = ArrayProto.every,
nativeSome = ArrayProto.some,
nativeIndexOf = ArrayProto.indexOf,
nativeLastIndexOf = ArrayProto.lastIndexOf,
nativeIsArray = <span class="hljs-built_in">Array</span>.isArray,
nativeKeys = <span class="hljs-built_in">Object</span>.keys,
nativeBind = FuncProto.bind;</pre></div></div>
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<p>Create a safe reference to the Underscore object for use below.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">var</span> _ = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj)</span> {</span>
<span class="hljs-keyword">if</span> (obj <span class="hljs-keyword">instanceof</span> _) <span class="hljs-keyword">return</span> obj;
<span class="hljs-keyword">if</span> (!(<span class="hljs-keyword">this</span> <span class="hljs-keyword">instanceof</span> _)) <span class="hljs-keyword">return</span> <span class="hljs-keyword">new</span> _(obj);
<span class="hljs-keyword">this</span>._wrapped = obj;
};</pre></div></div>
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<p>Export the Underscore object for <strong>Node.js</strong>, with
backwards-compatibility for the old <code>require()</code> API. If we’re in
the browser, add <code>_</code> as a global object via a string identifier,
for Closure Compiler “advanced” mode.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">if</span> (<span class="hljs-keyword">typeof</span> exports !== <span class="hljs-string">'undefined'</span>) {
<span class="hljs-keyword">if</span> (<span class="hljs-keyword">typeof</span> module !== <span class="hljs-string">'undefined'</span> && module.exports) {
exports = module.exports = _;
}
exports._ = _;
} <span class="hljs-keyword">else</span> {
root._ = _;
}</pre></div></div>
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<p>Current version.</p>
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<div class="content"><div class='highlight'><pre> _.VERSION = <span class="hljs-string">'1.6.0'</span>;</pre></div></div>
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<h2 id="collection-functions">Collection Functions</h2>
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<p>The cornerstone, an <code>each</code> implementation, aka <code>forEach</code>.
Handles objects with the built-in <code>forEach</code>, arrays, and raw objects.
Delegates to <strong>ECMAScript 5</strong>‘s native <code>forEach</code> if available.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">var</span> each = _.each = _.forEach = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj, iterator, context)</span> {</span>
<span class="hljs-keyword">if</span> (obj == <span class="hljs-literal">null</span>) <span class="hljs-keyword">return</span> obj;
<span class="hljs-keyword">if</span> (nativeForEach && obj.forEach === nativeForEach) {
obj.forEach(iterator, context);
} <span class="hljs-keyword">else</span> <span class="hljs-keyword">if</span> (obj.length === +obj.length) {
<span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> i = <span class="hljs-number">0</span>, length = obj.length; i < length; i++) {
<span class="hljs-keyword">if</span> (iterator.call(context, obj[i], i, obj) === breaker) <span class="hljs-keyword">return</span>;
}
} <span class="hljs-keyword">else</span> {
<span class="hljs-keyword">var</span> keys = _.keys(obj);
<span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> i = <span class="hljs-number">0</span>, length = keys.length; i < length; i++) {
<span class="hljs-keyword">if</span> (iterator.call(context, obj[keys[i]], keys[i], obj) === breaker) <span class="hljs-keyword">return</span>;
}
}
<span class="hljs-keyword">return</span> obj;
};</pre></div></div>
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<p>Return the results of applying the iterator to each element.
Delegates to <strong>ECMAScript 5</strong>‘s native <code>map</code> if available.</p>
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<div class="content"><div class='highlight'><pre> _.map = _.collect = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj, iterator, context)</span> {</span>
<span class="hljs-keyword">var</span> results = [];
<span class="hljs-keyword">if</span> (obj == <span class="hljs-literal">null</span>) <span class="hljs-keyword">return</span> results;
<span class="hljs-keyword">if</span> (nativeMap && obj.map === nativeMap) <span class="hljs-keyword">return</span> obj.map(iterator, context);
each(obj, <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(value, index, list)</span> {</span>
results.push(iterator.call(context, value, index, list));
});
<span class="hljs-keyword">return</span> results;
};
<span class="hljs-keyword">var</span> reduceError = <span class="hljs-string">'Reduce of empty array with no initial value'</span>;</pre></div></div>
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<p><strong>Reduce</strong> builds up a single result from a list of values, aka <code>inject</code>,
or <code>foldl</code>. Delegates to <strong>ECMAScript 5</strong>‘s native <code>reduce</code> if available.</p>
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<div class="content"><div class='highlight'><pre> _.reduce = _.foldl = _.inject = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj, iterator, memo, context)</span> {</span>
<span class="hljs-keyword">var</span> initial = <span class="hljs-built_in">arguments</span>.length > <span class="hljs-number">2</span>;
<span class="hljs-keyword">if</span> (obj == <span class="hljs-literal">null</span>) obj = [];
<span class="hljs-keyword">if</span> (nativeReduce && obj.reduce === nativeReduce) {
<span class="hljs-keyword">if</span> (context) iterator = _.bind(iterator, context);
<span class="hljs-keyword">return</span> initial ? obj.reduce(iterator, memo) : obj.reduce(iterator);
}
each(obj, <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(value, index, list)</span> {</span>
<span class="hljs-keyword">if</span> (!initial) {
memo = value;
initial = <span class="hljs-literal">true</span>;
} <span class="hljs-keyword">else</span> {
memo = iterator.call(context, memo, value, index, list);
}
});
<span class="hljs-keyword">if</span> (!initial) <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-built_in">TypeError</span>(reduceError);
<span class="hljs-keyword">return</span> memo;
};</pre></div></div>
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<p>The right-associative version of reduce, also known as <code>foldr</code>.
Delegates to <strong>ECMAScript 5</strong>‘s native <code>reduceRight</code> if available.</p>
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<div class="content"><div class='highlight'><pre> _.reduceRight = _.foldr = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj, iterator, memo, context)</span> {</span>
<span class="hljs-keyword">var</span> initial = <span class="hljs-built_in">arguments</span>.length > <span class="hljs-number">2</span>;
<span class="hljs-keyword">if</span> (obj == <span class="hljs-literal">null</span>) obj = [];
<span class="hljs-keyword">if</span> (nativeReduceRight && obj.reduceRight === nativeReduceRight) {
<span class="hljs-keyword">if</span> (context) iterator = _.bind(iterator, context);
<span class="hljs-keyword">return</span> initial ? obj.reduceRight(iterator, memo) : obj.reduceRight(iterator);
}
<span class="hljs-keyword">var</span> length = obj.length;
<span class="hljs-keyword">if</span> (length !== +length) {
<span class="hljs-keyword">var</span> keys = _.keys(obj);
length = keys.length;
}
each(obj, <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(value, index, list)</span> {</span>
index = keys ? keys[--length] : --length;
<span class="hljs-keyword">if</span> (!initial) {
memo = obj[index];
initial = <span class="hljs-literal">true</span>;
} <span class="hljs-keyword">else</span> {
memo = iterator.call(context, memo, obj[index], index, list);
}
});
<span class="hljs-keyword">if</span> (!initial) <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-built_in">TypeError</span>(reduceError);
<span class="hljs-keyword">return</span> memo;
};</pre></div></div>
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<p>Return the first value which passes a truth test. Aliased as <code>detect</code>.</p>
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<div class="content"><div class='highlight'><pre> _.find = _.detect = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj, predicate, context)</span> {</span>
<span class="hljs-keyword">var</span> result;
any(obj, <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(value, index, list)</span> {</span>
<span class="hljs-keyword">if</span> (predicate.call(context, value, index, list)) {
result = value;
<span class="hljs-keyword">return</span> <span class="hljs-literal">true</span>;
}
});
<span class="hljs-keyword">return</span> result;
};</pre></div></div>
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<p>Return all the elements that pass a truth test.
Delegates to <strong>ECMAScript 5</strong>‘s native <code>filter</code> if available.
Aliased as <code>select</code>.</p>
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<div class="content"><div class='highlight'><pre> _.filter = _.select = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj, predicate, context)</span> {</span>
<span class="hljs-keyword">var</span> results = [];
<span class="hljs-keyword">if</span> (obj == <span class="hljs-literal">null</span>) <span class="hljs-keyword">return</span> results;
<span class="hljs-keyword">if</span> (nativeFilter && obj.filter === nativeFilter) <span class="hljs-keyword">return</span> obj.filter(predicate, context);
each(obj, <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(value, index, list)</span> {</span>
<span class="hljs-keyword">if</span> (predicate.call(context, value, index, list)) results.push(value);
});
<span class="hljs-keyword">return</span> results;
};</pre></div></div>
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<p>Return all the elements for which a truth test fails.</p>
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<div class="content"><div class='highlight'><pre> _.reject = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj, predicate, context)</span> {</span>
<span class="hljs-keyword">return</span> _.filter(obj, <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(value, index, list)</span> {</span>
<span class="hljs-keyword">return</span> !predicate.call(context, value, index, list);
}, context);
};</pre></div></div>
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<p>Determine whether all of the elements match a truth test.
Delegates to <strong>ECMAScript 5</strong>‘s native <code>every</code> if available.
Aliased as <code>all</code>.</p>
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<div class="content"><div class='highlight'><pre> _.every = _.all = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj, predicate, context)</span> {</span>
predicate || (predicate = _.identity);
<span class="hljs-keyword">var</span> result = <span class="hljs-literal">true</span>;
<span class="hljs-keyword">if</span> (obj == <span class="hljs-literal">null</span>) <span class="hljs-keyword">return</span> result;
<span class="hljs-keyword">if</span> (nativeEvery && obj.every === nativeEvery) <span class="hljs-keyword">return</span> obj.every(predicate, context);
each(obj, <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(value, index, list)</span> {</span>
<span class="hljs-keyword">if</span> (!(result = result && predicate.call(context, value, index, list))) <span class="hljs-keyword">return</span> breaker;
});
<span class="hljs-keyword">return</span> !!result;
};</pre></div></div>
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<p>Determine if at least one element in the object matches a truth test.
Delegates to <strong>ECMAScript 5</strong>‘s native <code>some</code> if available.
Aliased as <code>any</code>.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">var</span> any = _.some = _.any = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj, predicate, context)</span> {</span>
predicate || (predicate = _.identity);
<span class="hljs-keyword">var</span> result = <span class="hljs-literal">false</span>;
<span class="hljs-keyword">if</span> (obj == <span class="hljs-literal">null</span>) <span class="hljs-keyword">return</span> result;
<span class="hljs-keyword">if</span> (nativeSome && obj.some === nativeSome) <span class="hljs-keyword">return</span> obj.some(predicate, context);
each(obj, <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(value, index, list)</span> {</span>
<span class="hljs-keyword">if</span> (result || (result = predicate.call(context, value, index, list))) <span class="hljs-keyword">return</span> breaker;
});
<span class="hljs-keyword">return</span> !!result;
};</pre></div></div>
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<p>Determine if the array or object contains a given value (using <code>===</code>).
Aliased as <code>include</code>.</p>
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<div class="content"><div class='highlight'><pre> _.contains = _.include = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj, target)</span> {</span>
<span class="hljs-keyword">if</span> (obj == <span class="hljs-literal">null</span>) <span class="hljs-keyword">return</span> <span class="hljs-literal">false</span>;
<span class="hljs-keyword">if</span> (nativeIndexOf && obj.indexOf === nativeIndexOf) <span class="hljs-keyword">return</span> obj.indexOf(target) != -<span class="hljs-number">1</span>;
<span class="hljs-keyword">return</span> any(obj, <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(value)</span> {</span>
<span class="hljs-keyword">return</span> value === target;
});
};</pre></div></div>
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<p>Invoke a method (with arguments) on every item in a collection.</p>
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<div class="content"><div class='highlight'><pre> _.invoke = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj, method)</span> {</span>
<span class="hljs-keyword">var</span> args = slice.call(<span class="hljs-built_in">arguments</span>, <span class="hljs-number">2</span>);
<span class="hljs-keyword">var</span> isFunc = _.isFunction(method);
<span class="hljs-keyword">return</span> _.map(obj, <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(value)</span> {</span>
<span class="hljs-keyword">return</span> (isFunc ? method : value[method]).apply(value, args);
});
};</pre></div></div>
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<p>Convenience version of a common use case of <code>map</code>: fetching a property.</p>
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<div class="content"><div class='highlight'><pre> _.pluck = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj, key)</span> {</span>
<span class="hljs-keyword">return</span> _.map(obj, _.property(key));
};</pre></div></div>
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<p>Convenience version of a common use case of <code>filter</code>: selecting only objects
containing specific <code>key:value</code> pairs.</p>
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<div class="content"><div class='highlight'><pre> _.where = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj, attrs)</span> {</span>
<span class="hljs-keyword">return</span> _.filter(obj, _.matches(attrs));
};</pre></div></div>
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<p>Convenience version of a common use case of <code>find</code>: getting the first object
containing specific <code>key:value</code> pairs.</p>
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<div class="content"><div class='highlight'><pre> _.findWhere = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj, attrs)</span> {</span>
<span class="hljs-keyword">return</span> _.find(obj, _.matches(attrs));
};</pre></div></div>
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<p>Return the maximum element or (element-based computation).
Can’t optimize arrays of integers longer than 65,535 elements.
See <a href="https://bugs.webkit.org/show_bug.cgi?id=80797">WebKit Bug 80797</a></p>
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<div class="content"><div class='highlight'><pre> _.max = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj, iterator, context)</span> {</span>
<span class="hljs-keyword">if</span> (!iterator && _.isArray(obj) && obj[<span class="hljs-number">0</span>] === +obj[<span class="hljs-number">0</span>] && obj.length < <span class="hljs-number">65535</span>) {
<span class="hljs-keyword">return</span> <span class="hljs-built_in">Math</span>.max.apply(<span class="hljs-built_in">Math</span>, obj);
}
<span class="hljs-keyword">var</span> result = -<span class="hljs-literal">Infinity</span>, lastComputed = -<span class="hljs-literal">Infinity</span>;
each(obj, <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(value, index, list)</span> {</span>
<span class="hljs-keyword">var</span> computed = iterator ? iterator.call(context, value, index, list) : value;
<span class="hljs-keyword">if</span> (computed > lastComputed) {
result = value;
lastComputed = computed;
}
});
<span class="hljs-keyword">return</span> result;
};</pre></div></div>
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<p>Return the minimum element (or element-based computation).</p>
</div>
<div class="content"><div class='highlight'><pre> _.min = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj, iterator, context)</span> {</span>
<span class="hljs-keyword">if</span> (!iterator && _.isArray(obj) && obj[<span class="hljs-number">0</span>] === +obj[<span class="hljs-number">0</span>] && obj.length < <span class="hljs-number">65535</span>) {
<span class="hljs-keyword">return</span> <span class="hljs-built_in">Math</span>.min.apply(<span class="hljs-built_in">Math</span>, obj);
}
<span class="hljs-keyword">var</span> result = <span class="hljs-literal">Infinity</span>, lastComputed = <span class="hljs-literal">Infinity</span>;
each(obj, <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(value, index, list)</span> {</span>
<span class="hljs-keyword">var</span> computed = iterator ? iterator.call(context, value, index, list) : value;
<span class="hljs-keyword">if</span> (computed < lastComputed) {
result = value;
lastComputed = computed;
}
});
<span class="hljs-keyword">return</span> result;
};</pre></div></div>
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<p>Shuffle an array, using the modern version of the
<a href="http://en.wikipedia.org/wiki/Fisher–Yates_shuffle">Fisher-Yates shuffle</a>.</p>
</div>
<div class="content"><div class='highlight'><pre> _.shuffle = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj)</span> {</span>
<span class="hljs-keyword">var</span> rand;
<span class="hljs-keyword">var</span> index = <span class="hljs-number">0</span>;
<span class="hljs-keyword">var</span> shuffled = [];
each(obj, <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(value)</span> {</span>
rand = _.random(index++);
shuffled[index - <span class="hljs-number">1</span>] = shuffled[rand];
shuffled[rand] = value;
});
<span class="hljs-keyword">return</span> shuffled;
};</pre></div></div>
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<p>Sample <strong>n</strong> random values from a collection.
If <strong>n</strong> is not specified, returns a single random element.
The internal <code>guard</code> argument allows it to work with <code>map</code>.</p>
</div>
<div class="content"><div class='highlight'><pre> _.sample = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj, n, guard)</span> {</span>
<span class="hljs-keyword">if</span> (n == <span class="hljs-literal">null</span> || guard) {
<span class="hljs-keyword">if</span> (obj.length !== +obj.length) obj = _.values(obj);
<span class="hljs-keyword">return</span> obj[_.random(obj.length - <span class="hljs-number">1</span>)];
}
<span class="hljs-keyword">return</span> _.shuffle(obj).slice(<span class="hljs-number">0</span>, <span class="hljs-built_in">Math</span>.max(<span class="hljs-number">0</span>, n));
};</pre></div></div>
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<p>An internal function to generate lookup iterators.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">var</span> lookupIterator = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(value)</span> {</span>
<span class="hljs-keyword">if</span> (value == <span class="hljs-literal">null</span>) <span class="hljs-keyword">return</span> _.identity;
<span class="hljs-keyword">if</span> (_.isFunction(value)) <span class="hljs-keyword">return</span> value;
<span class="hljs-keyword">return</span> _.property(value);
};</pre></div></div>
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<p>Sort the object’s values by a criterion produced by an iterator.</p>
</div>
<div class="content"><div class='highlight'><pre> _.sortBy = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj, iterator, context)</span> {</span>
iterator = lookupIterator(iterator);
<span class="hljs-keyword">return</span> _.pluck(_.map(obj, <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(value, index, list)</span> {</span>
<span class="hljs-keyword">return</span> {
value: value,
index: index,
criteria: iterator.call(context, value, index, list)
};
}).sort(<span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(left, right)</span> {</span>
<span class="hljs-keyword">var</span> a = left.criteria;
<span class="hljs-keyword">var</span> b = right.criteria;
<span class="hljs-keyword">if</span> (a !== b) {
<span class="hljs-keyword">if</span> (a > b || a === <span class="hljs-keyword">void</span> <span class="hljs-number">0</span>) <span class="hljs-keyword">return</span> <span class="hljs-number">1</span>;
<span class="hljs-keyword">if</span> (a < b || b === <span class="hljs-keyword">void</span> <span class="hljs-number">0</span>) <span class="hljs-keyword">return</span> -<span class="hljs-number">1</span>;
}
<span class="hljs-keyword">return</span> left.index - right.index;
}), <span class="hljs-string">'value'</span>);
};</pre></div></div>
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<p>An internal function used for aggregate “group by” operations.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">var</span> group = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(behavior)</span> {</span>
<span class="hljs-keyword">return</span> <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj, iterator, context)</span> {</span>
<span class="hljs-keyword">var</span> result = {};
iterator = lookupIterator(iterator);
each(obj, <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(value, index)</span> {</span>
<span class="hljs-keyword">var</span> key = iterator.call(context, value, index, obj);
behavior(result, key, value);
});
<span class="hljs-keyword">return</span> result;
};
};</pre></div></div>
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<p>Groups the object’s values by a criterion. Pass either a string attribute
to group by, or a function that returns the criterion.</p>
</div>
<div class="content"><div class='highlight'><pre> _.groupBy = group(<span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(result, key, value)</span> {</span>
_.has(result, key) ? result[key].push(value) : result[key] = [value];
});</pre></div></div>
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<p>Indexes the object’s values by a criterion, similar to <code>groupBy</code>, but for
when you know that your index values will be unique.</p>
</div>
<div class="content"><div class='highlight'><pre> _.indexBy = group(<span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(result, key, value)</span> {</span>
result[key] = value;
});</pre></div></div>
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<p>Counts instances of an object that group by a certain criterion. Pass
either a string attribute to count by, or a function that returns the
criterion.</p>
</div>
<div class="content"><div class='highlight'><pre> _.countBy = group(<span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(result, key)</span> {</span>
_.has(result, key) ? result[key]++ : result[key] = <span class="hljs-number">1</span>;
});</pre></div></div>
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<p>Use a comparator function to figure out the smallest index at which
an object should be inserted so as to maintain order. Uses binary search.</p>
</div>
<div class="content"><div class='highlight'><pre> _.sortedIndex = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(array, obj, iterator, context)</span> {</span>
iterator = lookupIterator(iterator);
<span class="hljs-keyword">var</span> value = iterator.call(context, obj);
<span class="hljs-keyword">var</span> low = <span class="hljs-number">0</span>, high = array.length;
<span class="hljs-keyword">while</span> (low < high) {
<span class="hljs-keyword">var</span> mid = (low + high) >>> <span class="hljs-number">1</span>;
iterator.call(context, array[mid]) < value ? low = mid + <span class="hljs-number">1</span> : high = mid;
}
<span class="hljs-keyword">return</span> low;
};</pre></div></div>
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<p>Safely create a real, live array from anything iterable.</p>
</div>
<div class="content"><div class='highlight'><pre> _.toArray = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj)</span> {</span>
<span class="hljs-keyword">if</span> (!obj) <span class="hljs-keyword">return</span> [];
<span class="hljs-keyword">if</span> (_.isArray(obj)) <span class="hljs-keyword">return</span> slice.call(obj);
<span class="hljs-keyword">if</span> (obj.length === +obj.length) <span class="hljs-keyword">return</span> _.map(obj, _.identity);
<span class="hljs-keyword">return</span> _.values(obj);
};</pre></div></div>
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<p>Return the number of elements in an object.</p>
</div>
<div class="content"><div class='highlight'><pre> _.size = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj)</span> {</span>
<span class="hljs-keyword">if</span> (obj == <span class="hljs-literal">null</span>) <span class="hljs-keyword">return</span> <span class="hljs-number">0</span>;
<span class="hljs-keyword">return</span> (obj.length === +obj.length) ? obj.length : _.keys(obj).length;
};</pre></div></div>
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<h2 id="array-functions">Array Functions</h2>
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<p>Get the first element of an array. Passing <strong>n</strong> will return the first N
values in the array. Aliased as <code>head</code> and <code>take</code>. The <strong>guard</strong> check
allows it to work with <code>_.map</code>.</p>
</div>
<div class="content"><div class='highlight'><pre> _.first = _.head = _.take = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(array, n, guard)</span> {</span>
<span class="hljs-keyword">if</span> (array == <span class="hljs-literal">null</span>) <span class="hljs-keyword">return</span> <span class="hljs-keyword">void</span> <span class="hljs-number">0</span>;
<span class="hljs-keyword">if</span> ((n == <span class="hljs-literal">null</span>) || guard) <span class="hljs-keyword">return</span> array[<span class="hljs-number">0</span>];
<span class="hljs-keyword">if</span> (n < <span class="hljs-number">0</span>) <span class="hljs-keyword">return</span> [];
<span class="hljs-keyword">return</span> slice.call(array, <span class="hljs-number">0</span>, n);
};</pre></div></div>
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<p>Returns everything but the last entry of the array. Especially useful on
the arguments object. Passing <strong>n</strong> will return all the values in
the array, excluding the last N. The <strong>guard</strong> check allows it to work with
<code>_.map</code>.</p>
</div>
<div class="content"><div class='highlight'><pre> _.initial = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(array, n, guard)</span> {</span>
<span class="hljs-keyword">return</span> slice.call(array, <span class="hljs-number">0</span>, array.length - ((n == <span class="hljs-literal">null</span>) || guard ? <span class="hljs-number">1</span> : n));
};</pre></div></div>
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<p>Get the last element of an array. Passing <strong>n</strong> will return the last N
values in the array. The <strong>guard</strong> check allows it to work with <code>_.map</code>.</p>
</div>
<div class="content"><div class='highlight'><pre> _.last = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(array, n, guard)</span> {</span>
<span class="hljs-keyword">if</span> (array == <span class="hljs-literal">null</span>) <span class="hljs-keyword">return</span> <span class="hljs-keyword">void</span> <span class="hljs-number">0</span>;
<span class="hljs-keyword">if</span> ((n == <span class="hljs-literal">null</span>) || guard) <span class="hljs-keyword">return</span> array[array.length - <span class="hljs-number">1</span>];
<span class="hljs-keyword">return</span> slice.call(array, <span class="hljs-built_in">Math</span>.max(array.length - n, <span class="hljs-number">0</span>));
};</pre></div></div>
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<p>Returns everything but the first entry of the array. Aliased as <code>tail</code> and <code>drop</code>.
Especially useful on the arguments object. Passing an <strong>n</strong> will return
the rest N values in the array. The <strong>guard</strong>
check allows it to work with <code>_.map</code>.</p>
</div>
<div class="content"><div class='highlight'><pre> _.rest = _.tail = _.drop = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(array, n, guard)</span> {</span>
<span class="hljs-keyword">return</span> slice.call(array, (n == <span class="hljs-literal">null</span>) || guard ? <span class="hljs-number">1</span> : n);
};</pre></div></div>
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<p>Trim out all falsy values from an array.</p>
</div>
<div class="content"><div class='highlight'><pre> _.compact = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(array)</span> {</span>
<span class="hljs-keyword">return</span> _.filter(array, _.identity);
};</pre></div></div>
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<p>Internal implementation of a recursive <code>flatten</code> function.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">var</span> flatten = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(input, shallow, output)</span> {</span>
<span class="hljs-keyword">if</span> (shallow && _.every(input, _.isArray)) {
<span class="hljs-keyword">return</span> concat.apply(output, input);
}
each(input, <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(value)</span> {</span>
<span class="hljs-keyword">if</span> (_.isArray(value) || _.isArguments(value)) {
shallow ? push.apply(output, value) : flatten(value, shallow, output);
} <span class="hljs-keyword">else</span> {
output.push(value);
}
});
<span class="hljs-keyword">return</span> output;
};</pre></div></div>
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<p>Flatten out an array, either recursively (by default), or just one level.</p>
</div>
<div class="content"><div class='highlight'><pre> _.flatten = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(array, shallow)</span> {</span>
<span class="hljs-keyword">return</span> flatten(array, shallow, []);
};</pre></div></div>
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<p>Return a version of the array that does not contain the specified value(s).</p>
</div>
<div class="content"><div class='highlight'><pre> _.without = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(array)</span> {</span>
<span class="hljs-keyword">return</span> _.difference(array, slice.call(<span class="hljs-built_in">arguments</span>, <span class="hljs-number">1</span>));
};</pre></div></div>
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<p>Split an array into two arrays: one whose elements all satisfy the given
predicate, and one whose elements all do not satisfy the predicate.</p>
</div>
<div class="content"><div class='highlight'><pre> _.partition = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(array, predicate)</span> {</span>
<span class="hljs-keyword">var</span> pass = [], fail = [];
each(array, <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(elem)</span> {</span>
(predicate(elem) ? pass : fail).push(elem);
});
<span class="hljs-keyword">return</span> [pass, fail];
};</pre></div></div>
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<p>Produce a duplicate-free version of the array. If the array has already
been sorted, you have the option of using a faster algorithm.
Aliased as <code>unique</code>.</p>
</div>
<div class="content"><div class='highlight'><pre> _.uniq = _.unique = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(array, isSorted, iterator, context)</span> {</span>
<span class="hljs-keyword">if</span> (_.isFunction(isSorted)) {
context = iterator;
iterator = isSorted;
isSorted = <span class="hljs-literal">false</span>;
}
<span class="hljs-keyword">var</span> initial = iterator ? _.map(array, iterator, context) : array;
<span class="hljs-keyword">var</span> results = [];
<span class="hljs-keyword">var</span> seen = [];
each(initial, <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(value, index)</span> {</span>
<span class="hljs-keyword">if</span> (isSorted ? (!index || seen[seen.length - <span class="hljs-number">1</span>] !== value) : !_.contains(seen, value)) {
seen.push(value);
results.push(array[index]);
}
});
<span class="hljs-keyword">return</span> results;
};</pre></div></div>
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<p>Produce an array that contains the union: each distinct element from all of
the passed-in arrays.</p>
</div>
<div class="content"><div class='highlight'><pre> _.union = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">()</span> {</span>
<span class="hljs-keyword">return</span> _.uniq(_.flatten(<span class="hljs-built_in">arguments</span>, <span class="hljs-literal">true</span>));
};</pre></div></div>
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<p>Produce an array that contains every item shared between all the
passed-in arrays.</p>
</div>
<div class="content"><div class='highlight'><pre> _.intersection = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(array)</span> {</span>
<span class="hljs-keyword">var</span> rest = slice.call(<span class="hljs-built_in">arguments</span>, <span class="hljs-number">1</span>);
<span class="hljs-keyword">return</span> _.filter(_.uniq(array), <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(item)</span> {</span>
<span class="hljs-keyword">return</span> _.every(rest, <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(other)</span> {</span>
<span class="hljs-keyword">return</span> _.contains(other, item);
});
});
};</pre></div></div>
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<p>Take the difference between one array and a number of other arrays.
Only the elements present in just the first array will remain.</p>
</div>
<div class="content"><div class='highlight'><pre> _.difference = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(array)</span> {</span>
<span class="hljs-keyword">var</span> rest = concat.apply(ArrayProto, slice.call(<span class="hljs-built_in">arguments</span>, <span class="hljs-number">1</span>));
<span class="hljs-keyword">return</span> _.filter(array, <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(value)</span>{</span> <span class="hljs-keyword">return</span> !_.contains(rest, value); });
};</pre></div></div>
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<p>Zip together multiple lists into a single array — elements that share
an index go together.</p>
</div>
<div class="content"><div class='highlight'><pre> _.zip = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">()</span> {</span>
<span class="hljs-keyword">var</span> length = _.max(_.pluck(<span class="hljs-built_in">arguments</span>, <span class="hljs-string">'length'</span>).concat(<span class="hljs-number">0</span>));
<span class="hljs-keyword">var</span> results = <span class="hljs-keyword">new</span> <span class="hljs-built_in">Array</span>(length);
<span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> i = <span class="hljs-number">0</span>; i < length; i++) {
results[i] = _.pluck(<span class="hljs-built_in">arguments</span>, <span class="hljs-string">''</span> + i);
}
<span class="hljs-keyword">return</span> results;
};</pre></div></div>
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<p>Converts lists into objects. Pass either a single array of <code>[key, value]</code>
pairs, or two parallel arrays of the same length — one of keys, and one of
the corresponding values.</p>
</div>
<div class="content"><div class='highlight'><pre> _.object = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(list, values)</span> {</span>
<span class="hljs-keyword">if</span> (list == <span class="hljs-literal">null</span>) <span class="hljs-keyword">return</span> {};
<span class="hljs-keyword">var</span> result = {};
<span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> i = <span class="hljs-number">0</span>, length = list.length; i < length; i++) {
<span class="hljs-keyword">if</span> (values) {
result[list[i]] = values[i];
} <span class="hljs-keyword">else</span> {
result[list[i][<span class="hljs-number">0</span>]] = list[i][<span class="hljs-number">1</span>];
}
}
<span class="hljs-keyword">return</span> result;
};</pre></div></div>
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<p>If the browser doesn’t supply us with indexOf (I’m looking at you, <strong>MSIE</strong>),
we need this function. Return the position of the first occurrence of an
item in an array, or -1 if the item is not included in the array.
Delegates to <strong>ECMAScript 5</strong>‘s native <code>indexOf</code> if available.
If the array is large and already in sort order, pass <code>true</code>
for <strong>isSorted</strong> to use binary search.</p>
</div>
<div class="content"><div class='highlight'><pre> _.indexOf = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(array, item, isSorted)</span> {</span>
<span class="hljs-keyword">if</span> (array == <span class="hljs-literal">null</span>) <span class="hljs-keyword">return</span> -<span class="hljs-number">1</span>;
<span class="hljs-keyword">var</span> i = <span class="hljs-number">0</span>, length = array.length;
<span class="hljs-keyword">if</span> (isSorted) {
<span class="hljs-keyword">if</span> (<span class="hljs-keyword">typeof</span> isSorted == <span class="hljs-string">'number'</span>) {
i = (isSorted < <span class="hljs-number">0</span> ? <span class="hljs-built_in">Math</span>.max(<span class="hljs-number">0</span>, length + isSorted) : isSorted);
} <span class="hljs-keyword">else</span> {
i = _.sortedIndex(array, item);
<span class="hljs-keyword">return</span> array[i] === item ? i : -<span class="hljs-number">1</span>;
}
}
<span class="hljs-keyword">if</span> (nativeIndexOf && array.indexOf === nativeIndexOf) <span class="hljs-keyword">return</span> array.indexOf(item, isSorted);
<span class="hljs-keyword">for</span> (; i < length; i++) <span class="hljs-keyword">if</span> (array[i] === item) <span class="hljs-keyword">return</span> i;
<span class="hljs-keyword">return</span> -<span class="hljs-number">1</span>;
};</pre></div></div>
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<p>Delegates to <strong>ECMAScript 5</strong>‘s native <code>lastIndexOf</code> if available.</p>
</div>
<div class="content"><div class='highlight'><pre> _.lastIndexOf = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(array, item, from)</span> {</span>
<span class="hljs-keyword">if</span> (array == <span class="hljs-literal">null</span>) <span class="hljs-keyword">return</span> -<span class="hljs-number">1</span>;
<span class="hljs-keyword">var</span> hasIndex = from != <span class="hljs-literal">null</span>;
<span class="hljs-keyword">if</span> (nativeLastIndexOf && array.lastIndexOf === nativeLastIndexOf) {
<span class="hljs-keyword">return</span> hasIndex ? array.lastIndexOf(item, from) : array.lastIndexOf(item);
}
<span class="hljs-keyword">var</span> i = (hasIndex ? from : array.length);
<span class="hljs-keyword">while</span> (i--) <span class="hljs-keyword">if</span> (array[i] === item) <span class="hljs-keyword">return</span> i;
<span class="hljs-keyword">return</span> -<span class="hljs-number">1</span>;
};</pre></div></div>
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<p>Generate an integer Array containing an arithmetic progression. A port of
the native Python <code>range()</code> function. See
<a href="http://docs.python.org/library/functions.html#range">the Python documentation</a>.</p>
</div>
<div class="content"><div class='highlight'><pre> _.range = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(start, stop, step)</span> {</span>
<span class="hljs-keyword">if</span> (<span class="hljs-built_in">arguments</span>.length <= <span class="hljs-number">1</span>) {
stop = start || <span class="hljs-number">0</span>;
start = <span class="hljs-number">0</span>;
}
step = <span class="hljs-built_in">arguments</span>[<span class="hljs-number">2</span>] || <span class="hljs-number">1</span>;
<span class="hljs-keyword">var</span> length = <span class="hljs-built_in">Math</span>.max(<span class="hljs-built_in">Math</span>.ceil((stop - start) / step), <span class="hljs-number">0</span>);
<span class="hljs-keyword">var</span> idx = <span class="hljs-number">0</span>;
<span class="hljs-keyword">var</span> range = <span class="hljs-keyword">new</span> <span class="hljs-built_in">Array</span>(length);
<span class="hljs-keyword">while</span>(idx < length) {
range[idx++] = start;
start += step;
}
<span class="hljs-keyword">return</span> range;
};</pre></div></div>
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<h2 id="function-ahem-functions">Function (ahem) Functions</h2>
</div>
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<p>Reusable constructor function for prototype setting.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">var</span> ctor = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">()</span>{</span>};</pre></div></div>
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<p>Create a function bound to a given object (assigning <code>this</code>, and arguments,
optionally). Delegates to <strong>ECMAScript 5</strong>‘s native <code>Function.bind</code> if
available.</p>
</div>
<div class="content"><div class='highlight'><pre> _.bind = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(func, context)</span> {</span>
<span class="hljs-keyword">var</span> args, bound;
<span class="hljs-keyword">if</span> (nativeBind && func.bind === nativeBind) <span class="hljs-keyword">return</span> nativeBind.apply(func, slice.call(<span class="hljs-built_in">arguments</span>, <span class="hljs-number">1</span>));
<span class="hljs-keyword">if</span> (!_.isFunction(func)) <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-built_in">TypeError</span>;
args = slice.call(<span class="hljs-built_in">arguments</span>, <span class="hljs-number">2</span>);
<span class="hljs-keyword">return</span> bound = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">()</span> {</span>
<span class="hljs-keyword">if</span> (!(<span class="hljs-keyword">this</span> <span class="hljs-keyword">instanceof</span> bound)) <span class="hljs-keyword">return</span> func.apply(context, args.concat(slice.call(<span class="hljs-built_in">arguments</span>)));
ctor.prototype = func.prototype;
<span class="hljs-keyword">var</span> self = <span class="hljs-keyword">new</span> ctor;
ctor.prototype = <span class="hljs-literal">null</span>;
<span class="hljs-keyword">var</span> result = func.apply(self, args.concat(slice.call(<span class="hljs-built_in">arguments</span>)));
<span class="hljs-keyword">if</span> (<span class="hljs-built_in">Object</span>(result) === result) <span class="hljs-keyword">return</span> result;
<span class="hljs-keyword">return</span> self;
};
};</pre></div></div>
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<p>Partially apply a function by creating a version that has had some of its
arguments pre-filled, without changing its dynamic <code>this</code> context. _ acts
as a placeholder, allowing any combination of arguments to be pre-filled.</p>
</div>
<div class="content"><div class='highlight'><pre> _.partial = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(func)</span> {</span>
<span class="hljs-keyword">var</span> boundArgs = slice.call(<span class="hljs-built_in">arguments</span>, <span class="hljs-number">1</span>);
<span class="hljs-keyword">return</span> <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">()</span> {</span>
<span class="hljs-keyword">var</span> position = <span class="hljs-number">0</span>;
<span class="hljs-keyword">var</span> args = boundArgs.slice();
<span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> i = <span class="hljs-number">0</span>, length = args.length; i < length; i++) {
<span class="hljs-keyword">if</span> (args[i] === _) args[i] = <span class="hljs-built_in">arguments</span>[position++];
}
<span class="hljs-keyword">while</span> (position < <span class="hljs-built_in">arguments</span>.length) args.push(<span class="hljs-built_in">arguments</span>[position++]);
<span class="hljs-keyword">return</span> func.apply(<span class="hljs-keyword">this</span>, args);
};
};</pre></div></div>
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<p>Bind a number of an object’s methods to that object. Remaining arguments
are the method names to be bound. Useful for ensuring that all callbacks
defined on an object belong to it.</p>
</div>
<div class="content"><div class='highlight'><pre> _.bindAll = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj)</span> {</span>
<span class="hljs-keyword">var</span> funcs = slice.call(<span class="hljs-built_in">arguments</span>, <span class="hljs-number">1</span>);
<span class="hljs-keyword">if</span> (funcs.length === <span class="hljs-number">0</span>) <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-built_in">Error</span>(<span class="hljs-string">'bindAll must be passed function names'</span>);
each(funcs, <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(f)</span> {</span> obj[f] = _.bind(obj[f], obj); });
<span class="hljs-keyword">return</span> obj;
};</pre></div></div>
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<p>Memoize an expensive function by storing its results.</p>
</div>
<div class="content"><div class='highlight'><pre> _.memoize = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(func, hasher)</span> {</span>
<span class="hljs-keyword">var</span> memo = {};
hasher || (hasher = _.identity);
<span class="hljs-keyword">return</span> <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">()</span> {</span>
<span class="hljs-keyword">var</span> key = hasher.apply(<span class="hljs-keyword">this</span>, <span class="hljs-built_in">arguments</span>);
<span class="hljs-keyword">return</span> _.has(memo, key) ? memo[key] : (memo[key] = func.apply(<span class="hljs-keyword">this</span>, <span class="hljs-built_in">arguments</span>));
};
};</pre></div></div>
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<p>Delays a function for the given number of milliseconds, and then calls
it with the arguments supplied.</p>
</div>
<div class="content"><div class='highlight'><pre> _.delay = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(func, wait)</span> {</span>
<span class="hljs-keyword">var</span> args = slice.call(<span class="hljs-built_in">arguments</span>, <span class="hljs-number">2</span>);
<span class="hljs-keyword">return</span> setTimeout(<span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">()</span>{</span> <span class="hljs-keyword">return</span> func.apply(<span class="hljs-literal">null</span>, args); }, wait);
};</pre></div></div>
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<p>Defers a function, scheduling it to run after the current call stack has
cleared.</p>
</div>
<div class="content"><div class='highlight'><pre> _.defer = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(func)</span> {</span>
<span class="hljs-keyword">return</span> _.delay.apply(_, [func, <span class="hljs-number">1</span>].concat(slice.call(<span class="hljs-built_in">arguments</span>, <span class="hljs-number">1</span>)));
};</pre></div></div>
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<p>Returns a function, that, when invoked, will only be triggered at most once
during a given window of time. Normally, the throttled function will run
as much as it can, without ever going more than once per <code>wait</code> duration;
but if you’d like to disable the execution on the leading edge, pass
<code>{leading: false}</code>. To disable execution on the trailing edge, ditto.</p>
</div>
<div class="content"><div class='highlight'><pre> _.throttle = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(func, wait, options)</span> {</span>
<span class="hljs-keyword">var</span> context, args, result;
<span class="hljs-keyword">var</span> timeout = <span class="hljs-literal">null</span>;
<span class="hljs-keyword">var</span> previous = <span class="hljs-number">0</span>;
options || (options = {});
<span class="hljs-keyword">var</span> later = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">()</span> {</span>
previous = options.leading === <span class="hljs-literal">false</span> ? <span class="hljs-number">0</span> : _.now();
timeout = <span class="hljs-literal">null</span>;
result = func.apply(context, args);
context = args = <span class="hljs-literal">null</span>;
};
<span class="hljs-keyword">return</span> <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">()</span> {</span>
<span class="hljs-keyword">var</span> now = _.now();
<span class="hljs-keyword">if</span> (!previous && options.leading === <span class="hljs-literal">false</span>) previous = now;
<span class="hljs-keyword">var</span> remaining = wait - (now - previous);
context = <span class="hljs-keyword">this</span>;
args = <span class="hljs-built_in">arguments</span>;
<span class="hljs-keyword">if</span> (remaining <= <span class="hljs-number">0</span>) {
clearTimeout(timeout);
timeout = <span class="hljs-literal">null</span>;
previous = now;
result = func.apply(context, args);
context = args = <span class="hljs-literal">null</span>;
} <span class="hljs-keyword">else</span> <span class="hljs-keyword">if</span> (!timeout && options.trailing !== <span class="hljs-literal">false</span>) {
timeout = setTimeout(later, remaining);
}
<span class="hljs-keyword">return</span> result;
};
};</pre></div></div>
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<p>Returns a function, that, as long as it continues to be invoked, will not
be triggered. The function will be called after it stops being called for
N milliseconds. If <code>immediate</code> is passed, trigger the function on the
leading edge, instead of the trailing.</p>
</div>
<div class="content"><div class='highlight'><pre> _.debounce = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(func, wait, immediate)</span> {</span>
<span class="hljs-keyword">var</span> timeout, args, context, timestamp, result;
<span class="hljs-keyword">var</span> later = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">()</span> {</span>
<span class="hljs-keyword">var</span> last = _.now() - timestamp;
<span class="hljs-keyword">if</span> (last < wait) {
timeout = setTimeout(later, wait - last);
} <span class="hljs-keyword">else</span> {
timeout = <span class="hljs-literal">null</span>;
<span class="hljs-keyword">if</span> (!immediate) {
result = func.apply(context, args);
context = args = <span class="hljs-literal">null</span>;
}
}
};
<span class="hljs-keyword">return</span> <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">()</span> {</span>
context = <span class="hljs-keyword">this</span>;
args = <span class="hljs-built_in">arguments</span>;
timestamp = _.now();
<span class="hljs-keyword">var</span> callNow = immediate && !timeout;
<span class="hljs-keyword">if</span> (!timeout) {
timeout = setTimeout(later, wait);
}
<span class="hljs-keyword">if</span> (callNow) {
result = func.apply(context, args);
context = args = <span class="hljs-literal">null</span>;
}
<span class="hljs-keyword">return</span> result;
};
};</pre></div></div>
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<p>Returns a function that will be executed at most one time, no matter how
often you call it. Useful for lazy initialization.</p>
</div>
<div class="content"><div class='highlight'><pre> _.once = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(func)</span> {</span>
<span class="hljs-keyword">var</span> ran = <span class="hljs-literal">false</span>, memo;
<span class="hljs-keyword">return</span> <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">()</span> {</span>
<span class="hljs-keyword">if</span> (ran) <span class="hljs-keyword">return</span> memo;
ran = <span class="hljs-literal">true</span>;
memo = func.apply(<span class="hljs-keyword">this</span>, <span class="hljs-built_in">arguments</span>);
func = <span class="hljs-literal">null</span>;
<span class="hljs-keyword">return</span> memo;
};
};</pre></div></div>
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<p>Returns the first function passed as an argument to the second,
allowing you to adjust arguments, run code before and after, and
conditionally execute the original function.</p>
</div>
<div class="content"><div class='highlight'><pre> _.wrap = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(func, wrapper)</span> {</span>
<span class="hljs-keyword">return</span> _.partial(wrapper, func);
};</pre></div></div>
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<p>Returns a function that is the composition of a list of functions, each
consuming the return value of the function that follows.</p>
</div>
<div class="content"><div class='highlight'><pre> _.compose = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">()</span> {</span>
<span class="hljs-keyword">var</span> funcs = <span class="hljs-built_in">arguments</span>;
<span class="hljs-keyword">return</span> <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">()</span> {</span>
<span class="hljs-keyword">var</span> args = <span class="hljs-built_in">arguments</span>;
<span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> i = funcs.length - <span class="hljs-number">1</span>; i >= <span class="hljs-number">0</span>; i--) {
args = [funcs[i].apply(<span class="hljs-keyword">this</span>, args)];
}
<span class="hljs-keyword">return</span> args[<span class="hljs-number">0</span>];
};
};</pre></div></div>
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<p>Returns a function that will only be executed after being called N times.</p>
</div>
<div class="content"><div class='highlight'><pre> _.after = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(times, func)</span> {</span>
<span class="hljs-keyword">return</span> <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">()</span> {</span>
<span class="hljs-keyword">if</span> (--times < <span class="hljs-number">1</span>) {
<span class="hljs-keyword">return</span> func.apply(<span class="hljs-keyword">this</span>, <span class="hljs-built_in">arguments</span>);
}
};
};</pre></div></div>
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<h2 id="object-functions">Object Functions</h2>
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<p>Retrieve the names of an object’s properties.
Delegates to <strong>ECMAScript 5</strong>‘s native <code>Object.keys</code></p>
</div>
<div class="content"><div class='highlight'><pre> _.keys = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj)</span> {</span>
<span class="hljs-keyword">if</span> (!_.isObject(obj)) <span class="hljs-keyword">return</span> [];
<span class="hljs-keyword">if</span> (nativeKeys) <span class="hljs-keyword">return</span> nativeKeys(obj);
<span class="hljs-keyword">var</span> keys = [];
<span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> key <span class="hljs-keyword">in</span> obj) <span class="hljs-keyword">if</span> (_.has(obj, key)) keys.push(key);
<span class="hljs-keyword">return</span> keys;
};</pre></div></div>
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<p>Retrieve the values of an object’s properties.</p>
</div>
<div class="content"><div class='highlight'><pre> _.values = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj)</span> {</span>
<span class="hljs-keyword">var</span> keys = _.keys(obj);
<span class="hljs-keyword">var</span> length = keys.length;
<span class="hljs-keyword">var</span> values = <span class="hljs-keyword">new</span> <span class="hljs-built_in">Array</span>(length);
<span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> i = <span class="hljs-number">0</span>; i < length; i++) {
values[i] = obj[keys[i]];
}
<span class="hljs-keyword">return</span> values;
};</pre></div></div>
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<p>Convert an object into a list of <code>[key, value]</code> pairs.</p>
</div>
<div class="content"><div class='highlight'><pre> _.pairs = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj)</span> {</span>
<span class="hljs-keyword">var</span> keys = _.keys(obj);
<span class="hljs-keyword">var</span> length = keys.length;
<span class="hljs-keyword">var</span> pairs = <span class="hljs-keyword">new</span> <span class="hljs-built_in">Array</span>(length);
<span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> i = <span class="hljs-number">0</span>; i < length; i++) {
pairs[i] = [keys[i], obj[keys[i]]];
}
<span class="hljs-keyword">return</span> pairs;
};</pre></div></div>
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<p>Invert the keys and values of an object. The values must be serializable.</p>
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<div class="content"><div class='highlight'><pre> _.invert = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj)</span> {</span>
<span class="hljs-keyword">var</span> result = {};
<span class="hljs-keyword">var</span> keys = _.keys(obj);
<span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> i = <span class="hljs-number">0</span>, length = keys.length; i < length; i++) {
result[obj[keys[i]]] = keys[i];
}
<span class="hljs-keyword">return</span> result;
};</pre></div></div>
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<p>Return a sorted list of the function names available on the object.
Aliased as <code>methods</code></p>
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<div class="content"><div class='highlight'><pre> _.functions = _.methods = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj)</span> {</span>
<span class="hljs-keyword">var</span> names = [];
<span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> key <span class="hljs-keyword">in</span> obj) {
<span class="hljs-keyword">if</span> (_.isFunction(obj[key])) names.push(key);
}
<span class="hljs-keyword">return</span> names.sort();
};</pre></div></div>
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<p>Extend a given object with all the properties in passed-in object(s).</p>
</div>
<div class="content"><div class='highlight'><pre> _.extend = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj)</span> {</span>
each(slice.call(<span class="hljs-built_in">arguments</span>, <span class="hljs-number">1</span>), <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(source)</span> {</span>
<span class="hljs-keyword">if</span> (source) {
<span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> prop <span class="hljs-keyword">in</span> source) {
obj[prop] = source[prop];
}
}
});
<span class="hljs-keyword">return</span> obj;
};</pre></div></div>
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<p>Return a copy of the object only containing the whitelisted properties.</p>
</div>
<div class="content"><div class='highlight'><pre> _.pick = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj)</span> {</span>
<span class="hljs-keyword">var</span> copy = {};
<span class="hljs-keyword">var</span> keys = concat.apply(ArrayProto, slice.call(<span class="hljs-built_in">arguments</span>, <span class="hljs-number">1</span>));
each(keys, <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(key)</span> {</span>
<span class="hljs-keyword">if</span> (key <span class="hljs-keyword">in</span> obj) copy[key] = obj[key];
});
<span class="hljs-keyword">return</span> copy;
};</pre></div></div>
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<p>Return a copy of the object without the blacklisted properties.</p>
</div>
<div class="content"><div class='highlight'><pre> _.omit = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj)</span> {</span>
<span class="hljs-keyword">var</span> copy = {};
<span class="hljs-keyword">var</span> keys = concat.apply(ArrayProto, slice.call(<span class="hljs-built_in">arguments</span>, <span class="hljs-number">1</span>));
<span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> key <span class="hljs-keyword">in</span> obj) {
<span class="hljs-keyword">if</span> (!_.contains(keys, key)) copy[key] = obj[key];
}
<span class="hljs-keyword">return</span> copy;
};</pre></div></div>
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<p>Fill in a given object with default properties.</p>
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<div class="content"><div class='highlight'><pre> _.defaults = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj)</span> {</span>
each(slice.call(<span class="hljs-built_in">arguments</span>, <span class="hljs-number">1</span>), <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(source)</span> {</span>
<span class="hljs-keyword">if</span> (source) {
<span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> prop <span class="hljs-keyword">in</span> source) {
<span class="hljs-keyword">if</span> (obj[prop] === <span class="hljs-keyword">void</span> <span class="hljs-number">0</span>) obj[prop] = source[prop];
}
}
});
<span class="hljs-keyword">return</span> obj;
};</pre></div></div>
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<p>Create a (shallow-cloned) duplicate of an object.</p>
</div>
<div class="content"><div class='highlight'><pre> _.clone = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj)</span> {</span>
<span class="hljs-keyword">if</span> (!_.isObject(obj)) <span class="hljs-keyword">return</span> obj;
<span class="hljs-keyword">return</span> _.isArray(obj) ? obj.slice() : _.extend({}, obj);
};</pre></div></div>
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<p>Invokes interceptor with the obj, and then returns obj.
The primary purpose of this method is to “tap into” a method chain, in
order to perform operations on intermediate results within the chain.</p>
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<div class="content"><div class='highlight'><pre> _.tap = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj, interceptor)</span> {</span>
interceptor(obj);
<span class="hljs-keyword">return</span> obj;
};</pre></div></div>
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<p>Internal recursive comparison function for <code>isEqual</code>.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">var</span> eq = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(a, b, aStack, bStack)</span> {</span></pre></div></div>
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<p>Identical objects are equal. <code>0 === -0</code>, but they aren’t identical.
See the <a href="http://wiki.ecmascript.org/doku.php?id=harmony:egal">Harmony <code>egal</code> proposal</a>.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">if</span> (a === b) <span class="hljs-keyword">return</span> a !== <span class="hljs-number">0</span> || <span class="hljs-number">1</span> / a == <span class="hljs-number">1</span> / b;</pre></div></div>
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<p>A strict comparison is necessary because <code>null == undefined</code>.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">if</span> (a == <span class="hljs-literal">null</span> || b == <span class="hljs-literal">null</span>) <span class="hljs-keyword">return</span> a === b;</pre></div></div>
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<p>Unwrap any wrapped objects.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">if</span> (a <span class="hljs-keyword">instanceof</span> _) a = a._wrapped;
<span class="hljs-keyword">if</span> (b <span class="hljs-keyword">instanceof</span> _) b = b._wrapped;</pre></div></div>
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<p>Compare <code>[[Class]]</code> names.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">var</span> className = toString.call(a);
<span class="hljs-keyword">if</span> (className != toString.call(b)) <span class="hljs-keyword">return</span> <span class="hljs-literal">false</span>;
<span class="hljs-keyword">switch</span> (className) {</pre></div></div>
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<p>Strings, numbers, dates, and booleans are compared by value.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">case</span> <span class="hljs-string">'[object String]'</span>:</pre></div></div>
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<p>Primitives and their corresponding object wrappers are equivalent; thus, <code>"5"</code> is
equivalent to <code>new String("5")</code>.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">return</span> a == <span class="hljs-built_in">String</span>(b);
<span class="hljs-keyword">case</span> <span class="hljs-string">'[object Number]'</span>:</pre></div></div>
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<p><code>NaN</code>s are equivalent, but non-reflexive. An <code>egal</code> comparison is performed for
other numeric values.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">return</span> a != +a ? b != +b : (a == <span class="hljs-number">0</span> ? <span class="hljs-number">1</span> / a == <span class="hljs-number">1</span> / b : a == +b);
<span class="hljs-keyword">case</span> <span class="hljs-string">'[object Date]'</span>:
<span class="hljs-keyword">case</span> <span class="hljs-string">'[object Boolean]'</span>:</pre></div></div>
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<p>Coerce dates and booleans to numeric primitive values. Dates are compared by their
millisecond representations. Note that invalid dates with millisecond representations
of <code>NaN</code> are not equivalent.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">return</span> +a == +b;</pre></div></div>
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<p>RegExps are compared by their source patterns and flags.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">case</span> <span class="hljs-string">'[object RegExp]'</span>:
<span class="hljs-keyword">return</span> a.source == b.source &&
a.global == b.global &&
a.multiline == b.multiline &&
a.ignoreCase == b.ignoreCase;
}
<span class="hljs-keyword">if</span> (<span class="hljs-keyword">typeof</span> a != <span class="hljs-string">'object'</span> || <span class="hljs-keyword">typeof</span> b != <span class="hljs-string">'object'</span>) <span class="hljs-keyword">return</span> <span class="hljs-literal">false</span>;</pre></div></div>
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<p>Assume equality for cyclic structures. The algorithm for detecting cyclic
structures is adapted from ES 5.1 section 15.12.3, abstract operation <code>JO</code>.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">var</span> length = aStack.length;
<span class="hljs-keyword">while</span> (length--) {</pre></div></div>
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<p>Linear search. Performance is inversely proportional to the number of
unique nested structures.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">if</span> (aStack[length] == a) <span class="hljs-keyword">return</span> bStack[length] == b;
}</pre></div></div>
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<p>Objects with different constructors are not equivalent, but <code>Object</code>s
from different frames are.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">var</span> aCtor = a.constructor, bCtor = b.constructor;
<span class="hljs-keyword">if</span> (aCtor !== bCtor && !(_.isFunction(aCtor) && (aCtor <span class="hljs-keyword">instanceof</span> aCtor) &&
_.isFunction(bCtor) && (bCtor <span class="hljs-keyword">instanceof</span> bCtor))
&& (<span class="hljs-string">'constructor'</span> <span class="hljs-keyword">in</span> a && <span class="hljs-string">'constructor'</span> <span class="hljs-keyword">in</span> b)) {
<span class="hljs-keyword">return</span> <span class="hljs-literal">false</span>;
}</pre></div></div>
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<p>Add the first object to the stack of traversed objects.</p>
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<div class="content"><div class='highlight'><pre> aStack.push(a);
bStack.push(b);
<span class="hljs-keyword">var</span> size = <span class="hljs-number">0</span>, result = <span class="hljs-literal">true</span>;</pre></div></div>
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<p>Recursively compare objects and arrays.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">if</span> (className == <span class="hljs-string">'[object Array]'</span>) {</pre></div></div>
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<p>Compare array lengths to determine if a deep comparison is necessary.</p>
</div>
<div class="content"><div class='highlight'><pre> size = a.length;
result = size == b.length;
<span class="hljs-keyword">if</span> (result) {</pre></div></div>
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<p>Deep compare the contents, ignoring non-numeric properties.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">while</span> (size--) {
<span class="hljs-keyword">if</span> (!(result = eq(a[size], b[size], aStack, bStack))) <span class="hljs-keyword">break</span>;
}
}
} <span class="hljs-keyword">else</span> {</pre></div></div>
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<p>Deep compare objects.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> key <span class="hljs-keyword">in</span> a) {
<span class="hljs-keyword">if</span> (_.has(a, key)) {</pre></div></div>
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<p>Count the expected number of properties.</p>
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<div class="content"><div class='highlight'><pre> size++;</pre></div></div>
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<p>Deep compare each member.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">if</span> (!(result = _.has(b, key) && eq(a[key], b[key], aStack, bStack))) <span class="hljs-keyword">break</span>;
}
}</pre></div></div>
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<p>Ensure that both objects contain the same number of properties.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">if</span> (result) {
<span class="hljs-keyword">for</span> (key <span class="hljs-keyword">in</span> b) {
<span class="hljs-keyword">if</span> (_.has(b, key) && !(size--)) <span class="hljs-keyword">break</span>;
}
result = !size;
}
}</pre></div></div>
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<p>Remove the first object from the stack of traversed objects.</p>
</div>
<div class="content"><div class='highlight'><pre> aStack.pop();
bStack.pop();
<span class="hljs-keyword">return</span> result;
};</pre></div></div>
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<p>Perform a deep comparison to check if two objects are equal.</p>
</div>
<div class="content"><div class='highlight'><pre> _.isEqual = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(a, b)</span> {</span>
<span class="hljs-keyword">return</span> eq(a, b, [], []);
};</pre></div></div>
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<p>Is a given array, string, or object empty?
An “empty” object has no enumerable own-properties.</p>
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<div class="content"><div class='highlight'><pre> _.isEmpty = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj)</span> {</span>
<span class="hljs-keyword">if</span> (obj == <span class="hljs-literal">null</span>) <span class="hljs-keyword">return</span> <span class="hljs-literal">true</span>;
<span class="hljs-keyword">if</span> (_.isArray(obj) || _.isString(obj)) <span class="hljs-keyword">return</span> obj.length === <span class="hljs-number">0</span>;
<span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> key <span class="hljs-keyword">in</span> obj) <span class="hljs-keyword">if</span> (_.has(obj, key)) <span class="hljs-keyword">return</span> <span class="hljs-literal">false</span>;
<span class="hljs-keyword">return</span> <span class="hljs-literal">true</span>;
};</pre></div></div>
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<p>Is a given value a DOM element?</p>
</div>
<div class="content"><div class='highlight'><pre> _.isElement = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj)</span> {</span>
<span class="hljs-keyword">return</span> !!(obj && obj.nodeType === <span class="hljs-number">1</span>);
};</pre></div></div>
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<p>Is a given value an array?
Delegates to ECMA5’s native Array.isArray</p>
</div>
<div class="content"><div class='highlight'><pre> _.isArray = nativeIsArray || <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj)</span> {</span>
<span class="hljs-keyword">return</span> toString.call(obj) == <span class="hljs-string">'[object Array]'</span>;
};</pre></div></div>
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<p>Is a given variable an object?</p>
</div>
<div class="content"><div class='highlight'><pre> _.isObject = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj)</span> {</span>
<span class="hljs-keyword">return</span> obj === <span class="hljs-built_in">Object</span>(obj);
};</pre></div></div>
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<p>Add some isType methods: isArguments, isFunction, isString, isNumber, isDate, isRegExp.</p>
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<div class="content"><div class='highlight'><pre> each([<span class="hljs-string">'Arguments'</span>, <span class="hljs-string">'Function'</span>, <span class="hljs-string">'String'</span>, <span class="hljs-string">'Number'</span>, <span class="hljs-string">'Date'</span>, <span class="hljs-string">'RegExp'</span>], <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(name)</span> {</span>
_[<span class="hljs-string">'is'</span> + name] = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj)</span> {</span>
<span class="hljs-keyword">return</span> toString.call(obj) == <span class="hljs-string">'[object '</span> + name + <span class="hljs-string">']'</span>;
};
});</pre></div></div>
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<p>Define a fallback version of the method in browsers (ahem, IE), where
there isn’t any inspectable “Arguments” type.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">if</span> (!_.isArguments(<span class="hljs-built_in">arguments</span>)) {
_.isArguments = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj)</span> {</span>
<span class="hljs-keyword">return</span> !!(obj && _.has(obj, <span class="hljs-string">'callee'</span>));
};
}</pre></div></div>
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<p>Optimize <code>isFunction</code> if appropriate.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">if</span> (<span class="hljs-keyword">typeof</span> (<span class="hljs-regexp">/./</span>) !== <span class="hljs-string">'function'</span>) {
_.isFunction = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj)</span> {</span>
<span class="hljs-keyword">return</span> <span class="hljs-keyword">typeof</span> obj === <span class="hljs-string">'function'</span>;
};
}</pre></div></div>
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<p>Is a given object a finite number?</p>
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<div class="content"><div class='highlight'><pre> _.isFinite = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj)</span> {</span>
<span class="hljs-keyword">return</span> <span class="hljs-built_in">isFinite</span>(obj) && !<span class="hljs-built_in">isNaN</span>(<span class="hljs-built_in">parseFloat</span>(obj));
};</pre></div></div>
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<p>Is the given value <code>NaN</code>? (NaN is the only number which does not equal itself).</p>
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<div class="content"><div class='highlight'><pre> _.isNaN = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj)</span> {</span>
<span class="hljs-keyword">return</span> _.isNumber(obj) && obj != +obj;
};</pre></div></div>
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<p>Is a given value a boolean?</p>
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<div class="content"><div class='highlight'><pre> _.isBoolean = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj)</span> {</span>
<span class="hljs-keyword">return</span> obj === <span class="hljs-literal">true</span> || obj === <span class="hljs-literal">false</span> || toString.call(obj) == <span class="hljs-string">'[object Boolean]'</span>;
};</pre></div></div>
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<p>Is a given value equal to null?</p>
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<div class="content"><div class='highlight'><pre> _.isNull = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj)</span> {</span>
<span class="hljs-keyword">return</span> obj === <span class="hljs-literal">null</span>;
};</pre></div></div>
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<p>Is a given variable undefined?</p>
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<div class="content"><div class='highlight'><pre> _.isUndefined = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj)</span> {</span>
<span class="hljs-keyword">return</span> obj === <span class="hljs-keyword">void</span> <span class="hljs-number">0</span>;
};</pre></div></div>
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<p>Shortcut function for checking if an object has a given property directly
on itself (in other words, not on a prototype).</p>
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<div class="content"><div class='highlight'><pre> _.has = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj, key)</span> {</span>
<span class="hljs-keyword">return</span> hasOwnProperty.call(obj, key);
};</pre></div></div>
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<h2 id="utility-functions">Utility Functions</h2>
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<p>Run Underscore.js in <em>noConflict</em> mode, returning the <code>_</code> variable to its
previous owner. Returns a reference to the Underscore object.</p>
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<div class="content"><div class='highlight'><pre> _.noConflict = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">()</span> {</span>
root._ = previousUnderscore;
<span class="hljs-keyword">return</span> <span class="hljs-keyword">this</span>;
};</pre></div></div>
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<p>Keep the identity function around for default iterators.</p>
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<div class="content"><div class='highlight'><pre> _.identity = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(value)</span> {</span>
<span class="hljs-keyword">return</span> value;
};
_.constant = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(value)</span> {</span>
<span class="hljs-keyword">return</span> <span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-params">()</span> {</span>
<span class="hljs-keyword">return</span> value;
};
};
_.property = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(key)</span> {</span>
<span class="hljs-keyword">return</span> <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj)</span> {</span>
<span class="hljs-keyword">return</span> obj[key];
};
};</pre></div></div>
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<p>Returns a predicate for checking whether an object has a given set of <code>key:value</code> pairs.</p>
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<div class="content"><div class='highlight'><pre> _.matches = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(attrs)</span> {</span>
<span class="hljs-keyword">return</span> <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj)</span> {</span>
<span class="hljs-keyword">if</span> (obj === attrs) <span class="hljs-keyword">return</span> <span class="hljs-literal">true</span>; <span class="hljs-comment">//avoid comparing an object to itself.</span>
<span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> key <span class="hljs-keyword">in</span> attrs) {
<span class="hljs-keyword">if</span> (attrs[key] !== obj[key])
<span class="hljs-keyword">return</span> <span class="hljs-literal">false</span>;
}
<span class="hljs-keyword">return</span> <span class="hljs-literal">true</span>;
}
};</pre></div></div>
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<p>Run a function <strong>n</strong> times.</p>
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<div class="content"><div class='highlight'><pre> _.times = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(n, iterator, context)</span> {</span>
<span class="hljs-keyword">var</span> accum = <span class="hljs-built_in">Array</span>(<span class="hljs-built_in">Math</span>.max(<span class="hljs-number">0</span>, n));
<span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> i = <span class="hljs-number">0</span>; i < n; i++) accum[i] = iterator.call(context, i);
<span class="hljs-keyword">return</span> accum;
};</pre></div></div>
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<p>Return a random integer between min and max (inclusive).</p>
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<div class="content"><div class='highlight'><pre> _.random = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(min, max)</span> {</span>
<span class="hljs-keyword">if</span> (max == <span class="hljs-literal">null</span>) {
max = min;
min = <span class="hljs-number">0</span>;
}
<span class="hljs-keyword">return</span> min + <span class="hljs-built_in">Math</span>.floor(<span class="hljs-built_in">Math</span>.random() * (max - min + <span class="hljs-number">1</span>));
};</pre></div></div>
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<p>A (possibly faster) way to get the current timestamp as an integer.</p>
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<div class="content"><div class='highlight'><pre> _.now = <span class="hljs-built_in">Date</span>.now || <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">()</span> {</span> <span class="hljs-keyword">return</span> <span class="hljs-keyword">new</span> <span class="hljs-built_in">Date</span>().getTime(); };</pre></div></div>
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<p>List of HTML entities for escaping.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">var</span> entityMap = {
<span class="hljs-built_in">escape</span>: {
<span class="hljs-string">'&'</span>: <span class="hljs-string">'&amp;'</span>,
<span class="hljs-string">'<'</span>: <span class="hljs-string">'&lt;'</span>,
<span class="hljs-string">'>'</span>: <span class="hljs-string">'&gt;'</span>,
<span class="hljs-string">'"'</span>: <span class="hljs-string">'&quot;'</span>,
<span class="hljs-string">"'"</span>: <span class="hljs-string">'&#x27;'</span>
}
};
entityMap.unescape = _.invert(entityMap.escape);</pre></div></div>
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<p>Regexes containing the keys and values listed immediately above.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">var</span> entityRegexes = {
<span class="hljs-built_in">escape</span>: <span class="hljs-keyword">new</span> <span class="hljs-built_in">RegExp</span>(<span class="hljs-string">'['</span> + _.keys(entityMap.escape).join(<span class="hljs-string">''</span>) + <span class="hljs-string">']'</span>, <span class="hljs-string">'g'</span>),
<span class="hljs-built_in">unescape</span>: <span class="hljs-keyword">new</span> <span class="hljs-built_in">RegExp</span>(<span class="hljs-string">'('</span> + _.keys(entityMap.unescape).join(<span class="hljs-string">'|'</span>) + <span class="hljs-string">')'</span>, <span class="hljs-string">'g'</span>)
};</pre></div></div>
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<p>Functions for escaping and unescaping strings to/from HTML interpolation.</p>
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<div class="content"><div class='highlight'><pre> _.each([<span class="hljs-string">'escape'</span>, <span class="hljs-string">'unescape'</span>], <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(method)</span> {</span>
_[method] = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(string)</span> {</span>
<span class="hljs-keyword">if</span> (string == <span class="hljs-literal">null</span>) <span class="hljs-keyword">return</span> <span class="hljs-string">''</span>;
<span class="hljs-keyword">return</span> (<span class="hljs-string">''</span> + string).replace(entityRegexes[method], <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(match)</span> {</span>
<span class="hljs-keyword">return</span> entityMap[method][match];
});
};
});</pre></div></div>
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<p>If the value of the named <code>property</code> is a function then invoke it with the
<code>object</code> as context; otherwise, return it.</p>
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<div class="content"><div class='highlight'><pre> _.result = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(object, property)</span> {</span>
<span class="hljs-keyword">if</span> (object == <span class="hljs-literal">null</span>) <span class="hljs-keyword">return</span> <span class="hljs-keyword">void</span> <span class="hljs-number">0</span>;
<span class="hljs-keyword">var</span> value = object[property];
<span class="hljs-keyword">return</span> _.isFunction(value) ? value.call(object) : value;
};</pre></div></div>
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<p>Add your own custom functions to the Underscore object.</p>
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<div class="content"><div class='highlight'><pre> _.mixin = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj)</span> {</span>
each(_.functions(obj), <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(name)</span> {</span>
<span class="hljs-keyword">var</span> func = _[name] = obj[name];
_.prototype[name] = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">()</span> {</span>
<span class="hljs-keyword">var</span> args = [<span class="hljs-keyword">this</span>._wrapped];
push.apply(args, <span class="hljs-built_in">arguments</span>);
<span class="hljs-keyword">return</span> result.call(<span class="hljs-keyword">this</span>, func.apply(_, args));
};
});
};</pre></div></div>
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<p>Generate a unique integer id (unique within the entire client session).
Useful for temporary DOM ids.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">var</span> idCounter = <span class="hljs-number">0</span>;
_.uniqueId = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(prefix)</span> {</span>
<span class="hljs-keyword">var</span> id = ++idCounter + <span class="hljs-string">''</span>;
<span class="hljs-keyword">return</span> prefix ? prefix + id : id;
};</pre></div></div>
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<p>By default, Underscore uses ERB-style template delimiters, change the
following template settings to use alternative delimiters.</p>
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<div class="content"><div class='highlight'><pre> _.templateSettings = {
evaluate : <span class="hljs-regexp">/<%([\s\S]+?)%>/g</span>,
interpolate : <span class="hljs-regexp">/<%=([\s\S]+?)%>/g</span>,
<span class="hljs-built_in">escape</span> : <span class="hljs-regexp">/<%-([\s\S]+?)%>/g</span>
};</pre></div></div>
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<p>When customizing <code>templateSettings</code>, if you don’t want to define an
interpolation, evaluation or escaping regex, we need one that is
guaranteed not to match.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">var</span> noMatch = <span class="hljs-regexp">/(.)^/</span>;</pre></div></div>
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<p>Certain characters need to be escaped so that they can be put into a
string literal.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">var</span> escapes = {
<span class="hljs-string">"'"</span>: <span class="hljs-string">"'"</span>,
<span class="hljs-string">'\\'</span>: <span class="hljs-string">'\\'</span>,
<span class="hljs-string">'\r'</span>: <span class="hljs-string">'r'</span>,
<span class="hljs-string">'\n'</span>: <span class="hljs-string">'n'</span>,
<span class="hljs-string">'\t'</span>: <span class="hljs-string">'t'</span>,
<span class="hljs-string">'\u2028'</span>: <span class="hljs-string">'u2028'</span>,
<span class="hljs-string">'\u2029'</span>: <span class="hljs-string">'u2029'</span>
};
<span class="hljs-keyword">var</span> escaper = <span class="hljs-regexp">/\\|'|\r|\n|\t|\u2028|\u2029/g</span>;</pre></div></div>
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<p>JavaScript micro-templating, similar to John Resig’s implementation.
Underscore templating handles arbitrary delimiters, preserves whitespace,
and correctly escapes quotes within interpolated code.</p>
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<div class="content"><div class='highlight'><pre> _.template = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(text, data, settings)</span> {</span>
<span class="hljs-keyword">var</span> render;
settings = _.defaults({}, settings, _.templateSettings);</pre></div></div>
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<p>Combine delimiters into one regular expression via alternation.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">var</span> matcher = <span class="hljs-keyword">new</span> <span class="hljs-built_in">RegExp</span>([
(settings.escape || noMatch).source,
(settings.interpolate || noMatch).source,
(settings.evaluate || noMatch).source
].join(<span class="hljs-string">'|'</span>) + <span class="hljs-string">'|$'</span>, <span class="hljs-string">'g'</span>);</pre></div></div>
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<p>Compile the template source, escaping string literals appropriately.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">var</span> index = <span class="hljs-number">0</span>;
<span class="hljs-keyword">var</span> source = <span class="hljs-string">"__p+='"</span>;
text.replace(matcher, <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(match, escape, interpolate, evaluate, offset)</span> {</span>
source += text.slice(index, offset)
.replace(escaper, <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(match)</span> {</span> <span class="hljs-keyword">return</span> <span class="hljs-string">'\\'</span> + escapes[match]; });
<span class="hljs-keyword">if</span> (<span class="hljs-built_in">escape</span>) {
source += <span class="hljs-string">"'+\n((__t=("</span> + <span class="hljs-built_in">escape</span> + <span class="hljs-string">"))==null?'':_.escape(__t))+\n'"</span>;
}
<span class="hljs-keyword">if</span> (interpolate) {
source += <span class="hljs-string">"'+\n((__t=("</span> + interpolate + <span class="hljs-string">"))==null?'':__t)+\n'"</span>;
}
<span class="hljs-keyword">if</span> (evaluate) {
source += <span class="hljs-string">"';\n"</span> + evaluate + <span class="hljs-string">"\n__p+='"</span>;
}
index = offset + match.length;
<span class="hljs-keyword">return</span> match;
});
source += <span class="hljs-string">"';\n"</span>;</pre></div></div>
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<p>If a variable is not specified, place data values in local scope.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">if</span> (!settings.variable) source = <span class="hljs-string">'with(obj||{}){\n'</span> + source + <span class="hljs-string">'}\n'</span>;
source = <span class="hljs-string">"var __t,__p='',__j=Array.prototype.join,"</span> +
<span class="hljs-string">"print=function(){__p+=__j.call(arguments,'');};\n"</span> +
source + <span class="hljs-string">"return __p;\n"</span>;
<span class="hljs-keyword">try</span> {
render = <span class="hljs-keyword">new</span> <span class="hljs-built_in">Function</span>(settings.variable || <span class="hljs-string">'obj'</span>, <span class="hljs-string">'_'</span>, source);
} <span class="hljs-keyword">catch</span> (e) {
e.source = source;
<span class="hljs-keyword">throw</span> e;
}
<span class="hljs-keyword">if</span> (data) <span class="hljs-keyword">return</span> render(data, _);
<span class="hljs-keyword">var</span> template = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(data)</span> {</span>
<span class="hljs-keyword">return</span> render.call(<span class="hljs-keyword">this</span>, data, _);
};</pre></div></div>
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<p>Provide the compiled function source as a convenience for precompilation.</p>
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<div class="content"><div class='highlight'><pre> template.source = <span class="hljs-string">'function('</span> + (settings.variable || <span class="hljs-string">'obj'</span>) + <span class="hljs-string">'){\n'</span> + source + <span class="hljs-string">'}'</span>;
<span class="hljs-keyword">return</span> template;
};</pre></div></div>
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<p>Add a “chain” function, which will delegate to the wrapper.</p>
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<div class="content"><div class='highlight'><pre> _.chain = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj)</span> {</span>
<span class="hljs-keyword">return</span> _(obj).chain();
};</pre></div></div>
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<h2 id="oop">OOP</h2>
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<p>If Underscore is called as a function, it returns a wrapped object that
can be used OO-style. This wrapper holds altered versions of all the
underscore functions. Wrapped objects may be chained.</p>
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<p>Helper function to continue chaining intermediate results.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">var</span> result = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(obj)</span> {</span>
<span class="hljs-keyword">return</span> <span class="hljs-keyword">this</span>._chain ? _(obj).chain() : obj;
};</pre></div></div>
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<p>Add all of the Underscore functions to the wrapper object.</p>
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<div class="content"><div class='highlight'><pre> _.mixin(_);</pre></div></div>
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<p>Add all mutator Array functions to the wrapper.</p>
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<div class="content"><div class='highlight'><pre> each([<span class="hljs-string">'pop'</span>, <span class="hljs-string">'push'</span>, <span class="hljs-string">'reverse'</span>, <span class="hljs-string">'shift'</span>, <span class="hljs-string">'sort'</span>, <span class="hljs-string">'splice'</span>, <span class="hljs-string">'unshift'</span>], <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(name)</span> {</span>
<span class="hljs-keyword">var</span> method = ArrayProto[name];
_.prototype[name] = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">()</span> {</span>
<span class="hljs-keyword">var</span> obj = <span class="hljs-keyword">this</span>._wrapped;
method.apply(obj, <span class="hljs-built_in">arguments</span>);
<span class="hljs-keyword">if</span> ((name == <span class="hljs-string">'shift'</span> || name == <span class="hljs-string">'splice'</span>) && obj.length === <span class="hljs-number">0</span>) <span class="hljs-keyword">delete</span> obj[<span class="hljs-number">0</span>];
<span class="hljs-keyword">return</span> result.call(<span class="hljs-keyword">this</span>, obj);
};
});</pre></div></div>
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<p>Add all accessor Array functions to the wrapper.</p>
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<div class="content"><div class='highlight'><pre> each([<span class="hljs-string">'concat'</span>, <span class="hljs-string">'join'</span>, <span class="hljs-string">'slice'</span>], <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(name)</span> {</span>
<span class="hljs-keyword">var</span> method = ArrayProto[name];
_.prototype[name] = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">()</span> {</span>
<span class="hljs-keyword">return</span> result.call(<span class="hljs-keyword">this</span>, method.apply(<span class="hljs-keyword">this</span>._wrapped, <span class="hljs-built_in">arguments</span>));
};
});
_.extend(_.prototype, {</pre></div></div>
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<p>Start chaining a wrapped Underscore object.</p>
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<div class="content"><div class='highlight'><pre> chain: <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">()</span> {</span>
<span class="hljs-keyword">this</span>._chain = <span class="hljs-literal">true</span>;
<span class="hljs-keyword">return</span> <span class="hljs-keyword">this</span>;
},</pre></div></div>
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<p>Extracts the result from a wrapped and chained object.</p>
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<div class="content"><div class='highlight'><pre> value: <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">()</span> {</span>
<span class="hljs-keyword">return</span> <span class="hljs-keyword">this</span>._wrapped;
}
});</pre></div></div>
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<p>AMD registration happens at the end for compatibility with AMD loaders
that may not enforce next-turn semantics on modules. Even though general
practice for AMD registration is to be anonymous, underscore registers
as a named module because, like jQuery, it is a base library that is
popular enough to be bundled in a third party lib, but not be part of
an AMD load request. Those cases could generate an error when an
anonymous define() is called outside of a loader request.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">if</span> (<span class="hljs-keyword">typeof</span> define === <span class="hljs-string">'function'</span> && define.amd) {
define(<span class="hljs-string">'underscore'</span>, [], <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">()</span> {</span>
<span class="hljs-keyword">return</span> _;
});
}
}).call(<span class="hljs-keyword">this</span>);</pre></div></div>
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