What Is a Regular Expression

A Regular Expression is a sequence of characters that defines a search pattern. It can be used to:

For example, if you want to check if a string contains only numbers, you can use a regular expression.

Example:

let pattern = /^\d+$/; // Matches strings with only digits let result = pattern.test(“12345”); console.log(result); // true

Why Use Regular Expressions?

Syntax

Regular Expressions in JavaScript can be created in two ways:

1. Using a Literal

let regex = /pattern/;

2. Using the RegExp Constructor

let regex = new RegExp(“pattern”);

Both methods are valid, but the literal syntax is more commonly used.

Example:

let regex = /hello/; // Matches the word “hello” let text = “hello world!”; console.log(regex.test(text)); // true