Javascript [Electronic resources] : The Definitive Guide (4th Edition) نسخه متنی

Availability

JavaScript 1.2; JScript 5.5; ECMAScript v3

Synopsis

array.shift( )

Returns

The former first element of the array.

Description

shift(
) removes
and returns the first element of array,
shifting all subsequent elements down one place to occupy the newly
vacant space at the start of the array. If the array is empty,
shift( ) does nothing and returns the
undefined value. Note that shift(
) does not create a new array; instead, it modifies
array directly.

shift( ) is similar to Array.pop(
), except it operates on the beginning of an array rather
than the end. shift( ) is often used in
conjunction with unshift( ).

Example

var a = [1, [2,3], 4]
a.shift(  );  // Returns 1; a = [[2,3], 4]
a.shift(  );  // Returns [2,3]; a = [4]

See Also

Array.pop( ), Array.unshift( )