URL获取并修改参数【转】

 function changeURLPar(url, ref, value) {
     var str = "";
     if (url.indexOf('?') != -1)
         str = url.substr(url.indexOf('?') + 1);
     else
         return url + "?" + ref + "=" + value;
     var returnurl = "";
     var setparam = "";
     var arr;
     var modify = "0";
     if (str.indexOf('&') != -1) {
         arr = str.split('&');
         for (i in arr) {
             if (arr[i].split('=')[0] == ref) {
                 setparam = value;
                 modify = "1";
             }
             else {
                 setparam = arr[i].split('=')[1];
             }
             returnurl = returnurl + arr[i].split('=')[0] + "=" + setparam + "&";
         }
         returnurl = returnurl.substr(0, returnurl.length - 1);
         if (modify == "0")
             if (returnurl == str)
                 returnurl = returnurl + "&" + ref + "=" + value;
     }
     else {
         if (str.indexOf('=') != -1) {
             arr = str.split('=');
             if (arr[0] == ref) {
                 setparam = value;
                 modify = "1";
             }
             else {
                 setparam = arr[1];
             }
             returnurl = arr[0] + "=" + setparam;
             if (modify == "0")
                 if (returnurl == str)
                     returnurl = returnurl + "&" + ref + "=" + value;
         }
         else
             returnurl = ref + "=" + value;
     }
     return url.substr(0, url.indexOf('?')) + "?" + returnurl;
 }