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(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
Specification |
---|
ECMAScript (ECMA-262) The definition of 'String.prototype.concat' in that specification. |
Browser compatibility
BCD tables only load in the browser