function getParam(key) {

    var tmp = location.search;

    tmp = decodeURIComponent(tmp);

    var index = tmp.indexOf(key);

    var length = key.length;

    var value;

    if(index != -1){

        var start = index+length+1;

        var end = tmp.indexOf('&',start);

        if(end == -1){

           value = tmp.slice(start);

        }

        else{

            value = tmp.slice(start,end);

        }

    }

    else{

        value = '';

    }

    return value;

}

console.log( getParam('userid') ); // xxx

setParam:function (url,key,val) {

        var link = url;

        var tmp = '';

        if(link.indexOf('?') >  ){

            tmp = link.substr( link.indexOf('?') );  // ?status=all

        }

        tmp = decodeURIComponent(tmp);

        link = decodeURIComponent(link);

        if(!tmp){

            link = link + '?' + key + '=' + val + '&';

        }

        else{

            var ind = tmp.indexOf(key);

            if(ind <  ){ // 不存在这个key

                ind = link.indexOf('?')+;

                var qianzhi = link.substr(,ind);

                var houzhi = link.substr(ind);

                link = qianzhi + key + '=' + val + '&' + houzhi;

            }

            else{  //已有这个key,则更新这个key对应的值

                ind = link.indexOf(key);

                var qianzhi = link.substr(,ind);

                var ind2 = link.indexOf('&',ind);

                var houzhi = link.substr(ind2);

                link = qianzhi + key + '=' + val + houzhi;

            }

        }

        return link;

    },

dropParam:function (url,key) {

        var link = url;

        var tmp = '';

        if(link.indexOf('?') >  ){

            tmp = link.substr( link.indexOf('?') );  // ?status=all

        }

        tmp = decodeURIComponent(tmp);

        link = decodeURIComponent(link);

        if(tmp){

            if( tmp.indexOf(key) >){

                var ind = link.indexOf(key);

                var qianzhi = link.substr(,ind);

                var ind2 = link.indexOf('&',ind);

                var houzhi = link.substr(ind2+);

                link = qianzhi+houzhi;

            }

        }

        return link;

    },