The join()
method creates and returns a new string by concatenating all of the elements in an array (or an array-like object), separated by commas or a specified separator string. If the array has only one item, then that item will be returned without using the separator.
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Syntax
arr.join([separator])
Parameters
separator
Optional- Specifies a string to separate each pair of adjacent elements 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. If arr.length
is 0
, the empty string is returned.
Description
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.
Examples
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']; a.join(); // 'Wind,Rain,Fire' a.join(', '); // 'Wind, Rain, Fire' a.join(' + '); // 'Wind + Rain + Fire' a.join(''); // 'WindRainFire'
Joining an array-like object
The following example joins array-like object (arguments
), by calling Function.prototype.call
on Array.prototype.join
.
function f(a, b, c) {
var s = Array.prototype.join.call(arguments);
console.log(s); // '
}
f(1, 'a', true);
//expected output: "1,a,true"
Specifications
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. |
Standard | |
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'Array.prototype.join' in that specification. |
Standard | |
ECMAScript Latest Draft (ECMA-262) The definition of 'Array.prototype.join' in that specification. |
Draft |
Browser compatibility
Desktop | Mobile | Server | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Basic support | Chrome Full support 1 | Edge Full support 12 | Firefox Full support 1 | IE Full support 5.5 | Opera Full support Yes | Safari Full support Yes | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support Yes | Firefox Android Full support 4 | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes | nodejs Full support Yes |
Legend
- Full support
- Full support