Array.prototype.concat()

  • Revision slug: JavaScript/Reference/Global_Objects/Array/concat
  • Revision title: Array concat method
  • Revision id: 26312
  • Created:
  • Creator: Maian
  • Is current revision? No
  • Comment values can be concat'd to, add another example

Revision Content

Summary

Returns a new array comprised of this array joined with other array(s) and/or value(s).

Method of Array
Implemented in: JavaScript 1.2, NES 3.0
ECMA Version: ECMA-262

Syntax

concat(value1, value2, ..., valueN)

Parameters

valueN 
Arrays and/or values to concatenate to this array.

Description

concat does not alter the original arrays, but returns a "one level deep" copy that contains copies of the same elements combined from the original arrays. Elements of the original arrays are copied into the new array as follows:

  • Object references (and not the actual object): concat copies object references into the new array. Both the original and new array refer to the same object. That is, if a referenced object is modified, the changes are visible to both the new and original arrays.
  • Strings and numbers (not String and Number objects): concat copies the values of strings and numbers into the new array.

Any operation on the new array will have no effect on the original arrays, and vice versa.

Examples

Example: Concatenating two arrays

The following code concatenates two arrays:

alpha = new Array("a", "b", "c");
numeric = new Array(1, 2, 3);
alphaNumeric = alpha.concat(numeric); // creates array ["a", "b", "c", 1, 2, 3]

Example: Concatenating three arrays

The following code concatenates three arrays:

num1 = [1, 2, 3];
num2 = [4, 5, 6];
num3 = [7, 8, 9];
nums = num1.concat(num2,num3) // creates array [1, 2, 3, 4, 5, 6, 7, 8, 9]

Example: Concatenating values to an array

The following code concatenates three values to an array:

alpha = ['a', 'b', 'c'];
alphaNumeric = alpha.concat(1, 2, 3); // creates array ["a", "b", "c", 1, 2, 3]

Revision Source

<p>
</p>
<h3 name="Summary"> Summary </h3>
<p>Returns a new array comprised of this array joined with other array(s) and/or value(s).
</p>
<table class="fullwidth-table">
<tbody><tr>
<td class="header" colspan="2">Method of <a href="en/Core_JavaScript_1.5_Reference/Global_Objects/Array">Array</a></td>
</tr>
<tr>
<td>Implemented in:</td>
<td>JavaScript 1.2, NES 3.0</td>
</tr>
<tr>
<td>ECMA Version:</td>
<td>ECMA-262</td>
</tr>
</tbody></table>
<h3 name="Syntax"> Syntax </h3>
<p><code>
concat(<i>value1</i>, <i>value2</i>, ..., <i>valueN</i>)
</code>
</p>
<h3 name="Parameters"> Parameters </h3>
<dl><dt> <code>value<i>N</i></code> </dt><dd> Arrays and/or values to concatenate to this array.
</dd></dl>
<h3 name="Description"> Description </h3>
<p><code>concat</code> does not alter the original arrays, but returns a "one level deep" copy that contains copies of the same elements combined from the original arrays. Elements of the original arrays are copied into the new array as follows:
</p>
<ul><li> Object references (and not the actual object): <code>concat</code> copies object references into the new array. Both the original and new array refer to the same object. That is, if a referenced object is modified, the changes are visible to both the new and original arrays.
</li></ul>
<ul><li> Strings and numbers (not <a href="en/Core_JavaScript_1.5_Reference/Global_Objects/String">String</a> and <a href="en/Core_JavaScript_1.5_Reference/Global_Objects/Number">Number</a> objects): <code>concat</code> copies the values of strings and numbers into the new array.
</li></ul>
<p>Any operation on the new array will have no effect on the original arrays, and vice versa.
</p>
<h3 name="Examples"> Examples </h3>
<h4 name="Example:_Concatenating_two_arrays"> Example: Concatenating two arrays </h4>
<p>The following code concatenates two arrays:
</p>
<pre class="eval">alpha = new Array("a", "b", "c");
numeric = new Array(1, 2, 3);
alphaNumeric = alpha.concat(numeric); // creates array ["a", "b", "c", 1, 2, 3]
</pre>
<h4 name="Example:_Concatenating_three_arrays"> Example: Concatenating three arrays </h4>
<p>The following code concatenates three arrays:
</p>
<pre class="eval">num1 = [1, 2, 3];
num2 = [4, 5, 6];
num3 = [7, 8, 9];
nums = num1.concat(num2,num3) // creates array [1, 2, 3, 4, 5, 6, 7, 8, 9]
</pre>
<h4 name="Example:_Concatenating_values_to_an_array"> Example: Concatenating values to an array </h4>
<p>The following code concatenates three values to an array:
</p>
<pre class="eval">alpha = ['a', 'b', 'c'];
alphaNumeric = alpha.concat(1, 2, 3); // creates array ["a", "b", "c", 1, 2, 3]
</pre>
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