underscore.js | |
---|---|
| (function() { |
Baseline setup | |
Establish the root object, | var root = this; |
Save the previous value of the | var previousUnderscore = root._; |
Establish the object that gets thrown to break out of a loop iteration. | var breaker = typeof StopIteration !== 'undefined' ? StopIteration : '__break__'; |
Save bytes in the minified (but not gzipped) version: | var ArrayProto = Array.prototype, ObjProto = Object.prototype; |
Create quick reference variables for speed access to core prototypes. | var slice = ArrayProto.slice,
unshift = ArrayProto.unshift,
toString = ObjProto.toString,
hasOwnProperty = ObjProto.hasOwnProperty,
propertyIsEnumerable = ObjProto.propertyIsEnumerable; |
All ECMAScript 5 native function implementations that we hope to use are declared here. | var
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 = Array.isArray,
nativeKeys = Object.keys; |
Create a safe reference to the Underscore object for use below. | var _ = function(obj) { return new wrapper(obj); }; |
Export the Underscore object for CommonJS. | if (typeof exports !== 'undefined') exports._ = _; |
Export Underscore to the global scope. | root._ = _; |
Current version. | _.VERSION = '1.1.2'; |
Collection Functions | |
The cornerstone, an | var each = _.each = _.forEach = function(obj, iterator, context) {
try {
if (nativeForEach && obj.forEach === nativeForEach) {
obj.forEach(iterator, context);
} else if (_.isNumber(obj.length)) {
for (var i = 0, l = obj.length; i < l; i++) iterator.call(context, obj[i], i, obj);
} else {
for (var key in obj) {
if (hasOwnProperty.call(obj, key)) iterator.call(context, obj[key], key, obj);
}
}
} catch(e) {
if (e != breaker) throw e;
}
return obj;
}; |
Return the results of applying the iterator to each element.
Delegates to ECMAScript 5's native | _.map = function(obj, iterator, context) {
if (nativeMap && obj.map === nativeMap) return obj.map(iterator, context);
var results = [];
each(obj, function(value, index, list) {
results[results.length] = iterator.call(context, value, index, list);
});
return results;
}; |
Reduce builds up a single result from a list of values, aka | _.reduce = _.foldl = _.inject = function(obj, iterator, memo, context) {
if (nativeReduce && obj.reduce === nativeReduce) {
if (context) iterator = _.bind(iterator, context);
return obj.reduce(iterator, memo);
}
each(obj, function(value, index, list) {
memo = iterator.call(context, memo, value, index, list);
});
return memo;
}; |
The right-associative version of reduce, also known as | _.reduceRight = _.foldr = function(obj, iterator, memo, context) {
if (nativeReduceRight && obj.reduceRight === nativeReduceRight) {
if (context) iterator = _.bind(iterator, context);
return obj.reduceRight(iterator, memo);
}
var reversed = (_.isArray(obj) ? obj.slice() : _.toArray(obj)).reverse();
return _.reduce(reversed, iterator, memo, context);
}; |
Return the first value which passes a truth test. Aliased as | _.find = _.detect = function(obj, iterator, context) {
var result;
each(obj, function(value, index, list) {
if (iterator.call(context, value, index, list)) {
result = value;
_.breakLoop();
}
});
return result;
}; |
Return all the elements that pass a truth test.
Delegates to ECMAScript 5's native | _.filter = _.select = function(obj, iterator, context) {
if (nativeFilter && obj.filter === nativeFilter) return obj.filter(iterator, context);
var results = [];
each(obj, function(value, index, list) {
if (iterator.call(context, value, index, list)) results[results.length] = value;
});
return results;
}; |
Return all the elements for which a truth test fails. | _.reject = function(obj, iterator, context) {
var results = [];
each(obj, function(value, index, list) {
if (!iterator.call(context, value, index, list)) results[results.length] = value;
});
return results;
}; |
Determine whether all of the elements match a truth test.
Delegates to ECMAScript 5's native | _.every = _.all = function(obj, iterator, context) {
iterator = iterator || _.identity;
if (nativeEvery && obj.every === nativeEvery) return obj.every(iterator, context);
var result = true;
each(obj, function(value, index, list) {
if (!(result = result && iterator.call(context, value, index, list))) _.breakLoop();
});
return result;
}; |
Determine if at least one element in the object matches a truth test.
Delegates to ECMAScript 5's native | _.some = _.any = function(obj, iterator, context) {
iterator = iterator || _.identity;
if (nativeSome && obj.some === nativeSome) return obj.some(iterator, context);
var result = false;
each(obj, function(value, index, list) {
if (result = iterator.call(context, value, index, list)) _.breakLoop();
});
return result;
}; |
Determine if a given value is included in the array or object using | _.include = _.contains = function(obj, target) {
if (nativeIndexOf && obj.indexOf === nativeIndexOf) return obj.indexOf(target) != -1;
var found = false;
each(obj, function(value) {
if (found = value === target) _.breakLoop();
});
return found;
}; |
Invoke a method (with arguments) on every item in a collection. | _.invoke = function(obj, method) {
var args = slice.call(arguments, 2);
return _.map(obj, function(value) {
return (method ? value[method] : value).apply(value, args);
});
}; |
Convenience version of a common use case of | _.pluck = function(obj, key) {
return _.map(obj, function(value){ return value[key]; });
}; |
Return the maximum element or (element-based computation). | _.max = function(obj, iterator, context) {
if (!iterator && _.isArray(obj)) return Math.max.apply(Math, obj);
var result = {computed : -Infinity};
each(obj, function(value, index, list) {
var computed = iterator ? iterator.call(context, value, index, list) : value;
computed >= result.computed && (result = {value : value, computed : computed});
});
return result.value;
}; |
Return the minimum element (or element-based computation). | _.min = function(obj, iterator, context) {
if (!iterator && _.isArray(obj)) return Math.min.apply(Math, obj);
var result = {computed : Infinity};
each(obj, function(value, index, list) {
var computed = iterator ? iterator.call(context, value, index, list) : value;
computed < result.computed && (result = {value : value, computed : computed});
});
return result.value;
}; |
Sort the object's values by a criterion produced by an iterator. | _.sortBy = function(obj, iterator, context) {
return _.pluck(_.map(obj, function(value, index, list) {
return {
value : value,
criteria : iterator.call(context, value, index, list)
};
}).sort(function(left, right) {
var a = left.criteria, b = right.criteria;
return a < b ? -1 : a > b ? 1 : 0;
}), 'value');
}; |
Use a comparator function to figure out at what index an object should be inserted so as to maintain order. Uses binary search. | _.sortedIndex = function(array, obj, iterator) {
iterator = iterator || _.identity;
var low = 0, high = array.length;
while (low < high) {
var mid = (low + high) >> 1;
iterator(array[mid]) < iterator(obj) ? low = mid + 1 : high = mid;
}
return low;
}; |
Safely convert anything iterable into a real, live array. | _.toArray = function(iterable) {
if (!iterable) return [];
if (iterable.toArray) return iterable.toArray();
if (_.isArray(iterable)) return iterable;
if (_.isArguments(iterable)) return slice.call(iterable);
return _.values(iterable);
}; |
Return the number of elements in an object. | _.size = function(obj) {
return _.toArray(obj).length;
}; |
Array Functions | |
Get the first element of an array. Passing n will return the first N
values in the array. Aliased as | _.first = _.head = function(array, n, guard) {
return n && !guard ? slice.call(array, 0, n) : array[0];
}; |
Returns everything but the first entry of the array. Aliased as | _.rest = _.tail = function(array, index, guard) {
return slice.call(array, _.isUndefined(index) || guard ? 1 : index);
}; |
Get the last element of an array. | _.last = function(array) {
return array[array.length - 1];
}; |
Trim out all falsy values from an array. | _.compact = function(array) {
return _.filter(array, function(value){ return !!value; });
}; |
Return a completely flattened version of an array. | _.flatten = function(array) {
return _.reduce(array, function(memo, value) {
if (_.isArray(value)) return memo.concat(_.flatten(value));
memo[memo.length] = value;
return memo;
}, []);
}; |
Return a version of the array that does not contain the specified value(s). | _.without = function(array) {
var values = slice.call(arguments, 1);
return _.filter(array, function(value){ return !_.include(values, value); });
}; |
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 | _.uniq = _.unique = function(array, isSorted) {
return _.reduce(array, function(memo, el, i) {
if (0 == i || (isSorted === true ? _.last(memo) != el : !_.include(memo, el))) memo[memo.length] = el;
return memo;
}, []);
}; |
Produce an array that contains every item shared between all the passed-in arrays. | _.intersect = function(array) {
var rest = slice.call(arguments, 1);
return _.filter(_.uniq(array), function(item) {
return _.every(rest, function(other) {
return _.indexOf(other, item) >= 0;
});
});
}; |
Zip together multiple lists into a single array -- elements that share an index go together. | _.zip = function() {
var args = slice.call(arguments);
var length = _.max(_.pluck(args, 'length'));
var results = new Array(length);
for (var i = 0; i < length; i++) results[i] = _.pluck(args, "" + i);
return results;
}; |
If the browser doesn't supply us with indexOf (I'm looking at you, MSIE),
we need this function. Return the position of the first occurence of an
item in an array, or -1 if the item is not included in the array.
Delegates to ECMAScript 5's native | _.indexOf = function(array, item) {
if (nativeIndexOf && array.indexOf === nativeIndexOf) return array.indexOf(item);
for (var i = 0, l = array.length; i < l; i++) if (array[i] === item) return i;
return -1;
}; |
Delegates to ECMAScript 5's native | _.lastIndexOf = function(array, item) {
if (nativeLastIndexOf && array.lastIndexOf === nativeLastIndexOf) return array.lastIndexOf(item);
var i = array.length;
while (i--) if (array[i] === item) return i;
return -1;
}; |
Generate an integer Array containing an arithmetic progression. A port of
the native Python | _.range = function(start, stop, step) {
var args = slice.call(arguments),
solo = args.length <= 1,
start = solo ? 0 : args[0],
stop = solo ? args[0] : args[1],
step = args[2] || 1,
len = Math.max(Math.ceil((stop - start) / step), 0),
idx = 0,
range = new Array(len);
while (idx < len) {
range[idx++] = start;
start += step;
}
return range;
}; |
Function (ahem) Functions | |
Create a function bound to a given object (assigning | _.bind = function(func, obj) {
var args = slice.call(arguments, 2);
return function() {
return func.apply(obj || {}, args.concat(slice.call(arguments)));
};
}; |
Bind all of an object's methods to that object. Useful for ensuring that all callbacks defined on an object belong to it. | _.bindAll = function(obj) {
var funcs = slice.call(arguments, 1);
if (funcs.length == 0) funcs = _.functions(obj);
each(funcs, function(f) { obj[f] = _.bind(obj[f], obj); });
return obj;
}; |
Memoize an expensive function by storing its results. | _.memoize = function(func, hasher) {
var memo = {};
hasher = hasher || _.identity;
return function() {
var key = hasher.apply(this, arguments);
return key in memo ? memo[key] : (memo[key] = func.apply(this, arguments));
};
}; |
Delays a function for the given number of milliseconds, and then calls it with the arguments supplied. | _.delay = function(func, wait) {
var args = slice.call(arguments, 2);
return setTimeout(function(){ return func.apply(func, args); }, wait);
}; |
Defers a function, scheduling it to run after the current call stack has cleared. | _.defer = function(func) {
return _.delay.apply(_, [func, 1].concat(slice.call(arguments, 1)));
}; |
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. | _.wrap = function(func, wrapper) {
return function() {
var args = [func].concat(slice.call(arguments));
return wrapper.apply(wrapper, args);
};
}; |
Returns a function that is the composition of a list of functions, each consuming the return value of the function that follows. | _.compose = function() {
var funcs = slice.call(arguments);
return function() {
var args = slice.call(arguments);
for (var i=funcs.length-1; i >= 0; i--) {
args = [funcs[i].apply(this, args)];
}
return args[0];
};
}; |
Object Functions | |
Retrieve the names of an object's properties.
Delegates to ECMAScript 5's native | _.keys = nativeKeys || function(obj) {
if (_.isArray(obj)) return _.range(0, obj.length);
var keys = [];
for (var key in obj) if (hasOwnProperty.call(obj, key)) keys[keys.length] = key;
return keys;
}; |
Retrieve the values of an object's properties. | _.values = function(obj) {
return _.map(obj, _.identity);
}; |
Return a sorted list of the function names available on the object.
Aliased as | _.functions = _.methods = function(obj) {
return _.filter(_.keys(obj), function(key){ return _.isFunction(obj[key]); }).sort();
}; |
Extend a given object with all the properties in passed-in object(s). | _.extend = function(obj) {
each(slice.call(arguments, 1), function(source) {
for (var prop in source) obj[prop] = source[prop];
});
return obj;
}; |
Create a (shallow-cloned) duplicate of an object. | _.clone = function(obj) {
return _.isArray(obj) ? obj.slice() : _.extend({}, obj);
}; |
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. | _.tap = function(obj, interceptor) {
interceptor(obj);
return obj;
}; |
Perform a deep comparison to check if two objects are equal. | _.isEqual = function(a, b) { |
Check object identity. | if (a === b) return true; |
Different types? | var atype = typeof(a), btype = typeof(b);
if (atype != btype) return false; |
Basic equality test (watch out for coercions). | if (a == b) return true; |
One is falsy and the other truthy. | if ((!a && b) || (a && !b)) return false; |
One of them implements an isEqual()? | if (a.isEqual) return a.isEqual(b); |
Check dates' integer values. | if (_.isDate(a) && _.isDate(b)) return a.getTime() === b.getTime(); |
Both are NaN? | if (_.isNaN(a) && _.isNaN(b)) return false; |
Compare regular expressions. | if (_.isRegExp(a) && _.isRegExp(b))
return a.source === b.source &&
a.global === b.global &&
a.ignoreCase === b.ignoreCase &&
a.multiline === b.multiline; |
If a is not an object by this point, we can't handle it. | if (atype !== 'object') return false; |
Check for different array lengths before comparing contents. | if (a.length && (a.length !== b.length)) return false; |
Nothing else worked, deep compare the contents. | var aKeys = _.keys(a), bKeys = _.keys(b); |
Different object sizes? | if (aKeys.length != bKeys.length) return false; |
Recursive comparison of contents. | for (var key in a) if (!(key in b) || !_.isEqual(a[key], b[key])) return false;
return true;
}; |
Is a given array or object empty? | _.isEmpty = function(obj) {
if (_.isArray(obj) || _.isString(obj)) return obj.length === 0;
for (var key in obj) if (hasOwnProperty.call(obj, key)) return false;
return true;
}; |
Is a given value a DOM element? | _.isElement = function(obj) {
return !!(obj && obj.nodeType == 1);
}; |
Is a given value an array? Delegates to ECMA5's native Array.isArray | _.isArray = nativeIsArray || function(obj) {
return !!(obj && obj.concat && obj.unshift && !obj.callee);
}; |
Is a given variable an arguments object? | _.isArguments = function(obj) {
return !!(obj && obj.callee);
}; |
Is a given value a function? | _.isFunction = function(obj) {
return !!(obj && obj.constructor && obj.call && obj.apply);
}; |
Is a given value a string? | _.isString = function(obj) {
return !!(obj === '' || (obj && obj.charCodeAt && obj.substr));
}; |
Is a given value a number? | _.isNumber = function(obj) {
return (obj === +obj) || (toString.call(obj) === '[object Number]');
}; |
Is a given value a boolean? | _.isBoolean = function(obj) {
return obj === true || obj === false;
}; |
Is a given value a date? | _.isDate = function(obj) {
return !!(obj && obj.getTimezoneOffset && obj.setUTCFullYear);
}; |
Is the given value a regular expression? | _.isRegExp = function(obj) {
return !!(obj && obj.test && obj.exec && (obj.ignoreCase || obj.ignoreCase === false));
}; |
Is the given value NaN -- this one is interesting. NaN != NaN, and isNaN(undefined) == true, so we make sure it's a number first. | _.isNaN = function(obj) {
return _.isNumber(obj) && isNaN(obj);
}; |
Is a given value equal to null? | _.isNull = function(obj) {
return obj === null;
}; |
Is a given variable undefined? | _.isUndefined = function(obj) {
return typeof obj == 'undefined';
}; |
Utility Functions | |
Run Underscore.js in noConflict mode, returning the | _.noConflict = function() {
root._ = previousUnderscore;
return this;
}; |
Keep the identity function around for default iterators. | _.identity = function(value) {
return value;
}; |
Run a function n times. | _.times = function (n, iterator, context) {
for (var i = 0; i < n; i++) iterator.call(context, i);
}; |
Break out of the middle of an iteration. | _.breakLoop = function() {
throw breaker;
}; |
Add your own custom functions to the Underscore object, ensuring that they're correctly added to the OOP wrapper as well. | _.mixin = function(obj) {
each(_.functions(obj), function(name){
addToWrapper(name, _[name] = obj[name]);
});
}; |
Generate a unique integer id (unique within the entire client session). Useful for temporary DOM ids. | var idCounter = 0;
_.uniqueId = function(prefix) {
var id = idCounter++;
return prefix ? prefix + id : id;
}; |
By default, Underscore uses ERB-style template delimiters, change the following template settings to use alternative delimiters. | _.templateSettings = {
evaluate : /<%([\s\S]+?)%>/g,
interpolate : /<%=([\s\S]+?)%>/g
}; |
JavaScript micro-templating, similar to John Resig's implementation. Underscore templating handles arbitrary delimiters, preserves whitespace, and correctly escapes quotes within interpolated code. | _.template = function(str, data) {
var c = _.templateSettings;
var tmpl = 'var __p=[],print=function(){__p.push.apply(__p,arguments);};' +
'with(obj||{}){__p.push(\'' +
str.replace(/'/g, "\\'")
.replace(c.interpolate, function(match, code) {
return "'," + code.replace(/\\'/g, "'") + ",'";
})
.replace(c.evaluate || null, function(match, code) {
return "');" + code.replace(/\\'/g, "'")
.replace(/[\r\n\t]/g, ' ') + "__p.push('";
})
.replace(/\r/g, '\\r')
.replace(/\n/g, '\\n')
.replace(/\t/g, '\\t')
+ "');}return __p.join('');";
var func = new Function('obj', tmpl);
return data ? func(data) : func;
}; |
The OOP Wrapper | |
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. | var wrapper = function(obj) { this._wrapped = obj; }; |
Expose | _.prototype = wrapper.prototype; |
Helper function to continue chaining intermediate results. | var result = function(obj, chain) {
return chain ? _(obj).chain() : obj;
}; |
A method to easily add functions to the OOP wrapper. | var addToWrapper = function(name, func) {
wrapper.prototype[name] = function() {
var args = slice.call(arguments);
unshift.call(args, this._wrapped);
return result(func.apply(_, args), this._chain);
};
}; |
Add all of the Underscore functions to the wrapper object. | _.mixin(_); |
Add all mutator Array functions to the wrapper. | each(['pop', 'push', 'reverse', 'shift', 'sort', 'splice', 'unshift'], function(name) {
var method = ArrayProto[name];
wrapper.prototype[name] = function() {
method.apply(this._wrapped, arguments);
return result(this._wrapped, this._chain);
};
}); |
Add all accessor Array functions to the wrapper. | each(['concat', 'join', 'slice'], function(name) {
var method = ArrayProto[name];
wrapper.prototype[name] = function() {
return result(method.apply(this._wrapped, arguments), this._chain);
};
}); |
Start chaining a wrapped Underscore object. | wrapper.prototype.chain = function() {
this._chain = true;
return this;
}; |
Extracts the result from a wrapped and chained object. | wrapper.prototype.value = function() {
return this._wrapped;
};
})();
|