url_parser.js

function(url, params) {
    var parser = document.createElement('a');
    parser.href = url;
    var chunks = [];
    for(var param in params) {
        chunks.push(encodeURIComponent(param) + "=" + encodeURIComponent(params[param]));
    }
    parser.search = (parser.search ? parser.search + '&' : '?') + chunks.join("&");
    return parser.href;
}