Using URL parameters in Javascript

This is a simple function to parse parameters out of a URL and return them as properties of an object:

  <script type="text/javascript">
  // example URL: http://example.com/script.html?foo=hello+world&bar=goodbye

  // function to parse the URL
  function getParams (url) {

    // split url into host/path and args, then split args into an array
    var argstr = url.split("?")[1] || '';
    var args = argstr.split("&");

    var params = new Object;

    // args will have len=1 even if split() returned empty, so fix that
    var length = args[0] ? args.length : 0;

    // loop args and load into object properties
    for ( var i=0; i<length; i++ ) {
      var p = args[i].split("=");
      params[p[0]] = unescape(p[1]).replace(/\+/g, ' ');
    }

    return(params);
  }

  // send it our URL
  var params = getParams(window.location.href);

  // use the parameters
  document.write("foo = " + params.foo + "<br>");
  document.write("bar = " + params.bar + "<br>");

  // output is:
  // foo = hello world
  // bar = goodbye
  </script>

Loading Javascript libraries on demand

I needed to load the Google visualization API, but only needed it under certain conditions. Not wanting the overhead if not needed, I looked around for a way for Javascript to include external libraries. Sadly, it appears this facility is lacking, so I came up with the following hack.

  // create the script element with no src set
  <script language="Javascript" type="text/javascript" id="google_jsapi"></script>
  ...
  // add the src to the script element
  if ( some_condition ) {
    document.getElementById('google_jsapi').src = 'http://www.google.com/jsapi';
  }
  ...
  // use the library
  window.onload = do_stuff();