Tips
-----

### Detecting Custom Types.

Type which `.pop()`/`.shift()` accept is string, a custom object or a custom constructor.

```javascript
function MyConstructor(){/*...*/};
args.pop(MyConstructor); // Pop only if the last argument is instantiate by `new MyConstructor()`

var MyObj = {/*...*/};
args.pop(MyObj); // Pop only if the last argument is create by `Object.create(MyObj)`
```

### Specify Multiple Types

There are two ways to specify 'or' condition for types.

1. Passing string joined by "|" (eg: `args.pop('string|number');` )
2. Passing array as type (eg: `args.pop(['string', MyCustomObj]);` )


### Want Array Always

Note that `.pop()`/`.shift()` methods returns values as array **only when multiple entries hit**.
If you want to make sure to keep values as array, use `[].concat()`.

```javascript
var args = argx(arguments);
var values = [].concat(args.pop(2, 'string') || []); // Always array.
```