isValidURL

1/**
2 * Checks whether a string is a valid URL.
3 *
4 * @param url - The string to validate.
5 * @returns True if the string is a valid URL, false otherwise.
6 */
7export function isValidURL(url: string): boolean {
8  try {
9    new URL(url);
10    return true;
11  } catch {
12    return false;
13  }
14}

• Standards-Based Validation

  Relies on the built-in URL constructor, which adheres to the WHATWG URL specification for reliable parsing.

• No Regex Complexity

  Avoids brittle regular expressions in favor of native parsing logic, reducing maintenance overhead.

• Robust Across Schemes

  Supports validation of various protocols such as http, https, ftp, and more.

• Safe and Efficient

  Gracefully handles invalid input using try/catch without causing runtime crashes or performance penalties.

Tests | Examples

1test('validates correct URLs', () => {
2  expect(isValidURL('https://example.com')).toBe(true);
3  expect(isValidURL('http://localhost:3000')).toBe(true);
4  expect(isValidURL('ftp://ftp.example.com')).toBe(true);
5  expect(isValidURL('https://sub.example.co.uk/path?query=123')).toBe(true);
6});
7
8test('invalidates incorrect URLs', () => {
9  expect(isValidURL('not a url')).toBe(false);
10  expect(isValidURL('htp:/example.com')).toBe(false);
11  expect(isValidURL('example.com')).toBe(false); // missing protocol
12  expect(isValidURL('http//:example.com')).toBe(false);
13});
14
15test('invalidates empty and malformed strings', () => {
16  expect(isValidURL('')).toBe(false);
17  expect(isValidURL('   ')).toBe(false);
18});

Common Use Cases

• User Input Validation

  Ensure URLs entered in forms (e.g., profile links, image sources) are well-formed before submission.

• Link Previews and Embeds

  Verify URLs before generating previews or embedding third-party content.

• Sanitization for Redirects

  Validate dynamic redirect targets to prevent open redirect vulnerabilities.

• Content Management Systems

  Validate links in CMS editors or markdown inputs before saving or rendering.

• Bookmarking and Link Storage

  Check that saved or imported URLs are valid and parseable before persisting them.