The concat()
method concatenates the string arguments to the calling string and returns a new string.
The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.
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
Specification | Status | Comment |
---|---|---|
ECMAScript 3rd Edition (ECMA-262) | Standard | Initial definition. Implemented in JavaScript 1.2. |
ECMAScript 5.1 (ECMA-262) The definition of 'String.prototype.concat' in that specification. |
Standard | |
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'String.prototype.concat' in that specification. |
Standard | |
ECMAScript Latest Draft (ECMA-262) The definition of 'String.prototype.concat' in that specification. |
Draft |
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.
Desktop | Mobile | Server | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
concat | Chrome Full support 1 | Edge Full support 12 | Firefox Full support 1 | IE Full support 4 | Opera Full support Yes | Safari Full support Yes | WebView Android Full support 1 | Chrome Android Full support 18 | Firefox Android Full support 4 | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support 1.0 | nodejs Full support Yes |
Legend
- Full support
- Full support