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string.concat

The concat() method concatenates the string arguments to the calling string and returns a new string.

Syntax

str.concat(string2[, string3, ..., stringN])

Parameters

string2...stringN
Strings to concatenate to this string.

Return value

A new string containing the combined text of the strings provided.

Description

The concat() function concatenates the string arguments to the calling string and returns a new string. Changes to the original string or the returned string don't affect the other. If the arguments are not of the type string, they are converted to string values before concatenating.

Examples

Using concat()

The following example combines strings into a new string.

var hello = 'Hello, ';
console.log(hello.concat('Kevin', '. Have a nice day.'));
/* Hello, Kevin. Have a nice day. */

var greetList = ['Hello', ' ', 'Venkat', '!'];
"".concat(...greetList); // "Hello Venkat!"

"".concat({}); // [object Object]
"".concat([]); // ""
"".concat(null); // "null"
"".concat(true); // "true"
"".concat(4, 5); // "45"

Performance

It is strongly recommended that the assignment operators (+, +=) are used instead of the concat() method.
According to this performance test, the assignment operators are several times faster.

Specifications

Browser compatibilityUpdate compatibility data on GitHub

Desktop
Chrome Edge Firefox Internet Explorer Opera Safari
Basic support Yes Yes 1 Yes Yes Yes
Mobile
Android webview Chrome for Android Edge Mobile Firefox for Android Opera for Android iOS Safari Samsung Internet
Basic support Yes Yes Yes 4 Yes Yes Yes
Server
Node.js
Basic support Yes

See also

© 2005–2018 Mozilla Developer Network and individual contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/concat