RegExp

`RegExp.prototype.test`

Executes a search for a match between a regular expression and a specified string, returning true or false

Syntax

JavaScript

regexp.test(str)

Parameters

Parameter	Type	Description
str	string	The string against which to match

Return Value

true if there is a match, false otherwise

Examples

Basic Usage

const regex = /\d+/;
console.log(regex.test('hello 42')); // true
console.log(regex.test('hello')); // false

Practical Example

const emailRegex = /^[\w.-]+@[\w.-]+\.[a-zA-Z]{2,}$/;
console.log(emailRegex.test('[email protected]')); // true
console.log(emailRegex.test('invalid')); // false

Advanced Usage

const hasUpperCase = /[A-Z]/;
const hasNumber = /\d/;
function isStrong(pw: string) {
  return hasUpperCase.test(pw) && hasNumber.test(pw) && pw.length >= 8;
}
console.log(isStrong('Hello123!')); // true

Understanding RegExp.prototype.test

The RegExp.prototype.test method in JavaScript executes a search for a match between a regular expression and a specified string, returning true or false. It belongs to the RegExp object and is one of the most widely used methods for working with regexp values in modern JavaScript and TypeScript applications.

The method signature is regexp.test(str). It accepts 1 parameter: str. When called, it returns true if there is a match, false otherwise. Understanding when and how to use test() helps you write more expressive, readable code.

Common use cases for RegExp.prototype.test include data transformation, input validation, API response processing, and building reusable utility functions. It works well alongside related methods like regexp-exec, string-match, string-search, enabling you to chain operations together for complex data manipulation pipelines.

Browser support for RegExp.prototype.test 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.