Util function that can append/delete a param in a query string. (pass in 1 param to delete that param)

AlterQueryString.js

function AlterQueryString(param, val) {
    var queryString = window.location.search.replace("?", "");
    var parameterListRaw = queryString == "" ? [] : queryString.split("&");
    var parameterList = {};
    for (var i = 0; i < parameterListRaw.length; i++) {
        var parameter = parameterListRaw[i].split("=");
        if (typeof val != 'undefined') {
            parameterList[parameter[0]] = parameter[1];
        } else if (param != parameter[0]) {
            parameterList[parameter[0]] = parameter[1];
        }
    }
    if (typeof val != 'undefined') {
        parameterList[param] = val;
    }

    var newQueryString = Object.keys(parameterList).length > 0 ? "?" : "";
    for (var item in parameterList) {
        if (parameterList.hasOwnProperty(item)) {
            newQueryString += item + "=" + parameterList[item] + "&";
        }
    }
    newQueryString = newQueryString.replace(/&$/, "");
    return location.origin + location.pathname + newQueryString;
}