The join() method joins all elements of an array into a string.


<var>str</var> = <var>arr</var>.join([<var>separator</var> = ','])


Optional. Specifies a string to separate each element of the array. The separator is converted to a string if necessary. If omitted, the array elements are separated with a comma. If separator is an empty string, all elements are joined without any characters in between them.

Return value

A string with all array elements joined.


The string conversions of all array elements are joined into one string. If an element is undefined or null, it is converted to the empty string.


Joining an array four different ways

The following example creates an array, a, with three elements, then joins the array four times: using the default separator, then a comma and a space, then a plus and an empty string.

var a = ['Wind', 'Rain', 'Fire'];
var myVar1 = a.join();      // assigns 'Wind,Rain,Fire' to myVar1
var myVar2 = a.join(', ');  // assigns 'Wind, Rain, Fire' to myVar2
var myVar3 = a.join(' + '); // assigns 'Wind + Rain + Fire' to myVar3
var myVar4 = a.join('');    // assigns 'WindRainFire' to myVar4


Specification Status Comment
ECMAScript 1st Edition (ECMA-262) Standard Initial definition. Implemented in JavaScript 1.1.
ECMAScript 5.1 (ECMA-262)
The definition of 'Array.prototype.join' in that specification.
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'Array.prototype.join' in that specification.
ECMAScript 2017 Draft (ECMA-262)
The definition of 'Array.prototype.join' in that specification.

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
Basic support 1.0 1.0 (1.7 or earlier) 5.5 (Yes) (Yes)
Feature Android Chrome for Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support (Yes) (Yes) (Yes) (Yes) (Yes) (Yes)

See also


© 2016 Mozilla Contributors
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.

Array JavaScript Method Prototype Reference