W3cubDocs

/JavaScript

string.concat

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

Syntax

str.concat(str2 [, ...strN])

Parameters

str2 [, ...strN]
Strings to concatenate to str.

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.

Performance

It is strongly recommended that the assignment operators (+, +=) are used instead of the concat() method.

Examples

Using concat()

The following example combines strings into a new string.

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

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

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

Specifications

Browser compatibilityUpdate compatibility data on GitHub

Desktop
Chrome Edge Firefox Internet Explorer Opera Safari
concat 1 12 1 4 4 1
Mobile
Android webview Chrome for Android Firefox for Android Opera for Android Safari on iOS Samsung Internet
concat 1 18 4 10.1 1 1.0
Server
Node.js
concat 0.1.100

See also

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