How to test if a URL string is absolute or relative?

Question

How can I test a URL if it is a relative or absolute path in Javascript or jQuery? I want to handle accordingly depending if the passed in URL is a local or external path.

Answer 1

You can use a try, catch block to help with this. Rather than using a regular expression, you can use the URL interface at every step.

isExternalUrl (urlString) {
  try {
    const url = new URL(urlString) // THROW ON MISSING SCHEME

    // DOES THIS URL ORIGINATE FROM THIS WEBSITE?
    if (url.origin !== new URL(document.URL, document.baseURI).origin) {
      return true // IS EXTERNAL URL
    }
  } catch (_e) {
    // THROWS WHEN URL DOES NOT HAVE A SCHEME
    new URL(urlString, document.baseURL) // THROW AN EXCEPTION IF THE URL IS TRULY MALFORMED IN SOME WAY
  }

  return false
}