String.prototype.concat()

The concat() method combines the text of one or more strings 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 combines the text from one or more strings and returns a new string. Changes to the text in one string do not affect the other string.

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"
"".concat({}); // [object Object]

Performance

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

Specifications

Browser compatibility

The compatibility table in this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.

See also

• Array.prototype.concat()
• Assignment operators