String includes()

Overview

String.prototype.includes() checks whether a string contains a substring, while startsWith() and endsWith() cover common boundary checks. These methods are usually clearer than older indexOf comparisons.

Browser support

Syntax

const url = 'https://example.com/api/users';

url.includes('api');       // true
url.startsWith('https');   // true
url.endsWith('/users');    // true

// Specifying the search start position
'hello world'.includes('world', 6); // true

Live demo

Use cases

• Keyword checks

  Detect whether user input, labels, or messages contain a particular term before branching UI behavior.

• Prefix and suffix validation

  Check file extensions, secure URLs, or naming conventions without manual slicing logic.

Cautions

Accessibility

• If text matching drives warnings or validation, make the feedback explicit and readable rather than relying on silent string checks.

Related links

• MDN Web Docs - String includes()
• Can I use - String includes()

Powered by web-features