Regular Expressions

Regular Expressions

A regular expression (RegExp) is a pattern used to search for text. It is written between slashes.

Creating a pattern

let pattern = /hello/;

This pattern matches the text "hello".

Basic usage

/hello/.test("say hello");   // true
/hello/.test("goodbye");     // false

Common methods

• test(): returns true/false if there is a match.
• exec(): returns match details or null.
• match(): string method that returns matches.

"hello world".match(/hello/); // ["hello"]

Flags

Flags come after the closing slash:

/hello/i.test("HELLO"); // true

Why use regex?

• Validate emails, phones, passwords.
• Search and replace text.
• Extract parts of strings.

TL;DR

• RegExp is a text pattern between slashes.
• test() checks for a match.
• Flags: i (case), g (all matches), m (multiline).
• Great for validation and search.