Test if links are external with jQuery / javascript?

Question

How do I test to see if links are external or internal? Please note:

1. I cannot hard code the local domain.
2. I cannot test for \"http\". I could just as

Answer 1

You forgot one, what if you use a relative path.

forexample: /test

        hostname = new RegExp(location.host);
            // Act on each link
            $('a').each(function(){

            // Store current link's url
            var url = $(this).attr("href");

            // Test if current host (domain) is in it
            if(hostname.test(url)){
               // If it's local...
               $(this).addClass('local');
            }
            else if(url.slice(0, 1) == "/"){
                $(this).addClass('local'); 
            }
            else if(url.slice(0, 1) == "#"){
                // It's an anchor link
                $(this).addClass('anchor'); 
            }
            else {
               // a link that does not contain the current host
               $(this).addClass('external');                        
            }
        });

There are also the issue of file downloads .zip (local en external) which could use the classes "local download" or "external download". But didn't found a solution for it yet.

Answer 2

var external = RegExp('^((f|ht)tps?:)?//(?!' + location.host + ')');

Usage:

external.test('some url'); // => true or false

Answer 3

I use this function for jQuery:

$.fn.isExternal = function() {
  var host = window.location.host;
  var link = $('<a>', {
    href: this.attr('href')
  })[0].hostname;
  return (link !== host);
};

Usage is: $('a').isExternal();

Example: https://codepen.io/allurewebsolutions/pen/ygJPgV

Answer 4

Yes, I believe you can retrieve the current domain name with location.href. Another possibility is to create a link element, set the src to / and then retrieving the canonical URL (this will retrieve the base URL if you use one, and not necessarily the domain name).

Also see this post: Get the full URI from the href property of a link

Answer 5

var comp = new RegExp(location.host);

$('a').each(function(){
   if(comp.test($(this).attr('href'))){
       // a link that contains the current host           
       $(this).addClass('local');
   }
   else{
       // a link that does not contain the current host
       $(this).addClass('external');
   }
});

Note: this is just a quick & dirty example. It would match all href="#anchor" links as external too. It might be improved by doing some extra RegExp checking.

---

Update 2016-11-17

This question still got a lot of traffic and I was told by a ton of people that this accepted solution will fail on several occasions. As I stated, this was a very quick and dirty answer to show the principal way how to solve this problem. A more sophisticated solution is to use the properties which are accessible on a <a> (anchor) element. Like @Daved already pointed out in this answer, the key is to compare the hostname with the current window.location.hostname. I would prefer to compare the hostname properties, because they never include the port which is included to the host property if it differs from 80.

So here we go:

$( 'a' ).each(function() {
  if( location.hostname === this.hostname || !this.hostname.length ) {
      $(this).addClass('local');
  } else {
      $(this).addClass('external');
  }
});

State of the art:

Array.from( document.querySelectorAll( 'a' ) ).forEach( a => {
    a.classList.add( location.hostname === a.hostname || !a.hostname.length ? 'local' : 'external' );
});

Answer 6

This doesn't exactly meet the "cannot hardcode my domain" prerequisite of the question, but I found this post searching for a similar solution, and in my case I could hard code my url. My concern was alerting users that they are leaving the site, but not if they are staying on site, including subdomains (example: blog.mysite.com, which would fail in most of these other answers). So here is my solution, which takes some bits from the top voted answers above:

Array.from( document.querySelectorAll( 'a' ) ).forEach( a => {
  a.classList.add( a.hostname.includes("mywebsite.com") ? 'local' : 'external' );
});

$("a").on("click", function(event) {
  if ($(this).hasClass('local')) {
    return;
  } else if ($(this).hasClass('external')) {
    if (!confirm("You are about leave the <My Website> website.")) {
      event.preventDefault();
    }
  }
});