JavaScript URI Objects

I started looking at a dashcode project the other day. Within a few minutes, I realised that I needed something like URI.pm, in order to resolve URIs into an absolute form. I had a quick look around and there didn’t seem to be anything code out there that does this.

So, I had a quick look at RFC 3986 and noticed that amongst other things it contains pseudo-code for parsing and resolving URLs. I coded it up first in Ruby, which took the pseudo-code almost word for word, and made some tests for it. Then I translated into JavaScript and figured out how to use Test.Simple.

The end result is js-uri, a small URI object. It does what I need at the moment.

  // Parsing.
  var some_uri = new URI("http://www.example.com/foo/bar");
  alert(some_uri.authority); // www.example.com
  alert(some_uri);           // http://www.example.com/foo/bar

  // Resolving.
  var blah      = new URI("blah");
  var blah_full = blah.resolve(some_uri);
  alert(blah_full);         // http://www.example.com/foo/blah

There’s quite a bit it doesn’t do yet.

• %-escaping and unescaping.
• Parsing the URL in more detail. It would be useful to pull out the query parameters and host / port for instance.
• For some reason, the tests only work in Firefox. Not sure why.

But hopefully it’s still useful.

In the process of developing the JavaScript, I spent ages tracking down one particular problem. I was trying to introduce new scope to define a couple of private helper functions:

  (function () {
      function merge(base, rel_path) { ... }

      function remove_dot_segments(path) { ... }

      URI.prototype.resolve = function (base) {
          var target = new URI();
          // ...
          return target;
      }
  })();

Looks perfectly legit right? It caused syntax errors in every browser I tried. Eventually, JSLint managed to tell me the problem: a missing semicolon after the URI.prototype.resolve definition. I hate JavaScript for trying to guess where the semicolon should go. Because it can get it so wrong like this.