get_set_url_param.js

function getURLParameter(name) {
    return decodeURIComponent(
        (RegExp('[?|&]'+name + '=' + '(.+?)(&|$)').exec(location.search)||[null,null])[1]
    );
}
function setURLParameter(name,value){
	var search,
        getParam = getURLParameter(name),
        isParamInUrl = (getParam !== null && getParam !== "" && getParam !== "null" && (typeof getParam === "string" && getParam.length > 0));

    	if(isParamInUrl){
		search =location.search.replace(new RegExp('([?|&]'+name + '=)' + '(.+?)(&|$)'),"$1"+encodeURIComponent(value)+"$3"); 
	}else if(location.search.length){
		search = location.search +'&'+name + '=' +encodeURIComponent(value);
	}else{
		search = '?'+name + '=' +encodeURIComponent(value);
	}
	History.pushState({state:History.getStateId()+1},document.title,search);
}