Check if a JavaScript string is a URL

Question

Is there a way in JavaScript to check if a string is a URL?

RegExes are excluded because the URL is most likely written like stackoverflow; that is to s

Answer 1

You can try to use URL constructor: if it doesn't throw, the string is a valid URL:

function isValidUrl(string) {
  try {
    new URL(string);
  } catch (_) {
    return false;  
  }

  return true;
}

The term 'URL' is defined in RFC 3886 (as URI); it must begin with a scheme name, and the scheme name is not limited to http/https.

Notable examples:

• www.google.com is not valid URL (missing scheme)
• javascript:void(0) is valid URL, although not an HTTP one
• http://.. is valid URL, with the host being ..; whether it resolves depends on your DNS
• https://google..com is valid URL, same as above

If you want to check whether a string is a valid HTTP URL:

function isValidHttpUrl(string) {
  let url;

  try {
    url = new URL(string);
  } catch (_) {
    return false;  
  }

  return url.protocol === "http:" || url.protocol === "https:";
}