Get Query String Variable Value in JavaScript

function getParameterByName(name)
{
    name = name.replace(/[\[]/, "\\\[")
        .replace(/[\]]/, "\\\]");
    var regexS = "[\\?&]" + name + "=([^&#]*)",
        regex = new RegExp(regexS),
        results = regex.exec(window.location.href);
    if(results == null)
    {
        return "";
    }
    else
    {
        return decodeURIComponent(results[1].replace(/\+/g, " "));
    }
}

Using in JavaScript

var param = getParameterByName('<param_name>') ;