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 easily be linking to my own site with an http absolute link.
3. I want to use jQuery / javascript, not css.

I suspect the answer lies somewhere in location.href, but the solution evades me.

Thanks!

---

Update: Thanks to jAndy, I've got a slightly modified version of what he answered:

        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) == "#"){
                // It's an anchor link
                $(this).addClass('anchor'); 
            }
            else {
               // a link that does not contain the current host
               $(this).addClass('external');                        
            }
        });

Answer 1

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: http://stackoverflow.com/questions/2639070/get-the-full-uri-from-the-href-property-of-a-link

Answer 2

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.

Answer 3

And the no-jQuery way

var nodes = document.getElementsByTagName("a"), i = nodes.length;
var regExp = new RegExp("//" + location.host + "($|/");
while(i--){
    var href = nodes[i].href;
    var isLocal = (href.substring(0,4) === "http") ? regExp.test(href) : true;
    alert(href + " is " + (isLocal ? "local" : "not local"));
}

All hrefs not beginning with http (http://, https://) are automatically treated as local

Answer 4

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

Usage:

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