String

`String.prototype.concat`

Concatenates the string arguments to the calling string and returns a new string

Syntax

JavaScript

string.concat(...strings)

Parameters

Parameter	Type	Description
strings	string[]	Strings to concatenate to this string

Return Value

A new string containing the combined text

Examples

Basic Usage

const hello = 'Hello';
console.log(hello.concat(' ', 'World')); // 'Hello World'

Practical Example

const a = 'foo';
const b = a.concat('bar', 'baz');
console.log(b); // 'foobarbaz'

Advanced Usage

// Template literals are preferred over concat:
const name = 'World';
console.log(`Hello ${name}`); // 'Hello World'

Understanding String.prototype.concat

The String.prototype.concat method in JavaScript concatenates the string arguments to the calling string and returns a new string. It belongs to the String object and is one of the most widely used methods for working with string values in modern JavaScript and TypeScript applications.

The method signature is string.concat(...strings). It accepts 1 parameter: strings. When called, it returns a new string containing the combined text. Understanding when and how to use concat() helps you write more expressive, readable code.

Common use cases for String.prototype.concat include data transformation, input validation, API response processing, and building reusable utility functions. It works well alongside related methods like array-concat, string-slice, string-repeat, enabling you to chain operations together for complex data manipulation pipelines.

Browser support for String.prototype.concat is excellent across all modern browsers including Chrome, Firefox, Safari, and Edge. It is also fully supported in Node.js and Deno. For older environments, transpilation with Babel or a polyfill may be needed.