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JavaScript: The Definitive Guide, Fourth Edition
book

JavaScript: The Definitive Guide, Fourth Edition

by David Flanagan
November 2001
Intermediate to advanced content levelIntermediate to advanced
936 pages
68h 43m
English
O'Reilly Media, Inc.
Content preview from JavaScript: The Definitive Guide, Fourth Edition

Name

Array.unshift( ) — insert elements at the beginning of an array

Availability

JavaScript 1.2; JScript 5.5; ECMAScript v3

Synopsis

                  array.unshift(value, ...)

Arguments

value, ...

One or more values that are to be inserted at the start of array.

Returns

The new length of the array.

Description

unshift( ) inserts its arguments at the beginning of array, shifting the existing elements to higher indexes to make room. The first argument to shift( ) becomes the new element 0 of the array, the second argument, if any, becomes the new element 1, and so on. Note that unshift( ) does not create a new array; it modifies array directly.

Example

unshift( ) is often used in conjunction with shift( ). For example:

var a = [];             // a:[]
a.unshift(1);           // a:[1]          Returns: 1
a.unshift(22);          // a:[22,1]       Returns: 2
a.shift(  );            // a:[1]          Returns: 22
a.unshift(33,[4,5]);    // a:[33,[4,5],1] Returns: 3

See Also

Array.shift( )

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Publisher Resources

ISBN: 0596000480Supplemental ContentCatalog PageErrata