buildUrl.js

function buildUrl(url, parameters){
    var query = window.location.search.substring(1), vars = query.split('&'), qs = "";
    if (vars.length) {
        for(var j in vars) {
            if (vars[j] !== "") {
                var value = vars[j].split("=");
                if (parameters.hasOwnProperty(value[0]) === false) {
                    parameters[value[0]] = value[1];
                }
            }
        }
    }
    for(var key in parameters) {
        qs += encodeURIComponent(key) + "=" + encodeURIComponent(parameters[key]) + "&";
    }
    if (qs.length > 0){
        qs = qs.substring(0, qs.length-1); //chop off last "&"
        url = url + "?" + qs;
    }
    return url;
}