JavaScript Interview Question #186

What are regular expressions in JavaScript?

Advanced JavaScript, Practical Problems & Senior Interview Scenarios Senior Advanced

Quick Interview Answer

A regular expression describes a text pattern used for searching, matching, validation, extraction, and replacement. JavaScript supports regex literals and the RegExp constructor.

Detailed Explanation

A regular expression describes a text pattern used for searching, matching, validation, extraction, and replacement. JavaScript supports regex literals and the RegExp constructor.

Regular expressions are useful for well-defined text patterns, but complex validation rules can become difficult to read and maintain. Input validation should also consider business rules rather than relying only on a pattern.

Code Example

const emailLike =
    /^[^\s@]+@[^\s@]+\.[^\s@]+$/;

console.log(
    emailLike.test("user@example.com")
); // true

const text = "Order 12345";
console.log(text.match(/\d+/)?.[0]); // 12345