function getQueryVariable(variable) {

    var query = window.location.search.substring(1);
    var vars = query.split("&");

    for (var i=0;i<vars.length;i++) {
        var pair = vars[i].split("=");
        if (pair[0] == variable) {
            return pair[1];
        }
    }

    return "";
}

//  alert( getQueryVariable("x") );

function setQueryStringVar(queryString, varName, varValue) {

    found = false;
    newQueryString = "";

    queryVars = queryString.split("&");
        
    for (i=0;i<queryVars.length;i++) {

        if( i > 0 ){
            newQueryString += "&";
        }

        itemVar = queryVars[i].split("=");

        if( itemVar.length > 1 ){

            newQueryString += itemVar[0] + "=";

            if (itemVar[0] == varName) {
                newQueryString += varValue;
                found = true;
            }else{
                newQueryString += itemVar[1];
            }
        }
    }

    if( !found ){
        newQueryString += "&" + varName + "=" + varValue;
    }
    
    return newQueryString;
}