JavaScript: The Definitive Guide, Fourth Edition

Name

Array.shift( ) — shift array elements down

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( )