This is a really great function written in jQuery to determine the value of a url field:
$.urlParam = function(name){
var results = new RegExp('[\\?&]' + name + '=([^&#]*)').exec(window.location.href);
return results[1] || 0;
}
// example.com?someparam=name&otherparam=8&id=6
$.urlParam('someparam'); // name
$.urlParam('id'); // 6
$.urlParam('notavar'); // null
if (results == null) {
return 0;
} else {
return results[1] || 0;
}