Mastering Regular Expressions (Regex) in JS

Regular expressions (regex) are sequences of characters that define a search pattern. They are extremely useful for validating user inputs (like emails or passwords), extracting substrings, or replacing content inside text fields.

Creating a Regex in JavaScript

Regex can be defined using literal notation enclosed in slashes or by calling the RegExp constructor:

const pattern1 = /ab+c/i;
const pattern2 = new RegExp("ab+c", "i"); // "i" is flag for case-insensitivity

Common Methods

• regex.test(str): Returns a boolean indicating if the pattern exists in the string.
• str.match(regex): Returns an array of matches or null.
• str.replace(regex, replacement): Replaces matches with a new string.

const emailPattern = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
console.log(emailPattern.test("user@domain.com")); // true