get parameters value from url query string

javascript

function getParams(param) {
    var search = window.location.search;
    if (search == "") return;
    else {
        var varsList = search.slice(1).split(/&(?:amp;)*/);
        for (var i = varsList.length - 1; i >= 0; i--) {
            var equalArray = varsList[i].split("=");
            if (equalArray[0] == param) return equalArray[1];
        }
    }
}