jquery url dynamic change

app.js

 url =  window.location.href;
    paramName = 'myparam';
        paramValue = $(this).val();
        var pattern = new RegExp('('+paramName+'=).*?(&|$)') 
        var newUrl = url.replace(pattern,'$1' + paramValue + '$2');
        var n=url.indexOf(paramName);
        alert(n)
        if(n == -1){
            newUrl = newUrl + (newUrl.indexOf('?')>0 ? '&' : '?') + paramName + '=' + paramValue 
        }
        window.history.pushState('title', active_tab, newUrl);