# Yahoo! UI Library

### collection 3.0.0

Yahoo! UI Library > collection > YUI~array~extras
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## Class YUI~array~extras

Adds the following array utilities to the YUI instance (Y.Array). This is in addition to the methods provided in the core.

### Properties

#### lastIndexOf - `static object`

Returns the index of the last item in the array that contains the specified value, -1 if the value isn't found. method Array.lastIndexOf

### Methods

#### Array.every

`static boolean Array.every ( a , f , o )`
Executes the supplied function on each item in the array.

Parameters:
  `a <Array>` the array to iterate
  `f <Function>` the function to execute on each item
  `o <object>` Optional context object

Returns: `boolean`
  true if every item in the array returns true from the supplied function.

#### Array.filter

`static Array Array.filter ( a , f , o )`
Executes the supplied function on each item in the array. Returns a new array containing the items that the supplied function returned true for.

Parameters:
  `a <Array>` the array to iterate
  `f <Function>` the function to execute on each item
  `o <object>` Optional context object

Returns: `Array`
  The items on which the supplied function returned true. If no items matched an empty array is returned.

#### Array.find

`static object Array.find ( a , f , o )`
Executes the supplied function on each item in the array, searching for the first item that matches the supplied function.

Parameters:
  `a <Array>` the array to search
  `f <Function>` the function to execute on each item. Iteration is stopped as soon as this function returns true on an item.
  `o <object>` Optional context object

Returns: `object`
  the first item that the supplied function returns true for, or null if it never returns true

#### Array.grep

`static Array Array.grep ( a , pattern )`
Iterates over an array, returning a new array of all the elements that match the supplied regular expression

Parameters:
  `a <Array>` a collection to iterate over
  `pattern <RegExp>` The regular expression to test against each item

Returns: `Array`
  All the items in the collection that produce a match against the supplied regular expression. If no items match, an empty array is returned.

#### Array.map

`static Array Array.map ( a , f , o )`
Executes the supplied function on each item in the array.

Parameters:
  `a <Array>` the array to iterate
  `f <Function>` the function to execute on each item
  `o <object>` Optional context object

Returns: `Array`
  A new array containing the return value of the supplied function for each item in the original array.

#### Array.partition

`static Array.partition ( a , o )`
Partitions an array into two new arrays, one with the items that match the supplied function, and one with the items that do not.

Parameters:
  `a <Array>` a collection to iterate over
  `o <object>` Optional execution context of f.

Returns: ``
  An object with two members, 'matches' and 'rejects', that are arrays containing the items that were selected or rejected by the test function (or an empty array).

#### Array.reduce

`static Array.reduce ( a , init , f , o )`
Executes the supplied function on each item in the array. Reduce "folds" the array into a single value.

Parameters:
  `a <Array>` the array to iterate
  `init <object>` The initial value to start from
  `f <Function>` the function to execute on each item. It is responsible for returning the updated value of the computation.
  `o <object>` Optional context object

Returns: ``
  A value that results from iteratively applying the supplied function to each element in the array.

#### Array.reject

`static Array Array.reject ( a , f , o )`
The inverse of filter. Executes the supplied function on each item. Returns a new array containing the items that the supplied function returned *false* for.

Parameters:
  `a <Array>` the array to iterate
  `f <Function>` the function to execute on each item
  `o <object>` Optional context object

Returns: `Array`
  The items on which the supplied function returned false.

#### Array.unique

`static Array Array.unique ( a , sort )`
Returns a copy of the array with the duplicate entries removed

Parameters:
  `a <Array>` the array to find the subset of uniques for
  `sort <bool>` flag to denote if the array is sorted or not. Defaults to false, the more general operation

Returns: `Array`
  a copy of the array with duplicate entries removed

#### Array.zip

`static Array.zip ( a , a2 )`
Creates an array of arrays by pairing the corresponding elements of two arrays together into a new array.

Parameters:
  `a <Array>` a collection to iterate over
  `a2 <Array>` another collection whose members will be paired with members of the first parameter

Returns: ``
  An array of arrays formed by pairing each element of the first collection with an item in the second collection having the corresponding index.

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