JavaScript:QueryString(zz加解释)

function QueryString(fieldName)
{  
        //假设document.location.herf=http://localhost/myweb/default.aspx?info=1&name=2,fiedName=info
  var urlString = document.location.search;//urlString为?info=1&name=2
    if(urlString != null)
 {
          var typeQu = fieldName+"=";
          var urlEnd = urlString.indexOf(typeQu);//寻找info=1位置,为1
       
            if(urlEnd != -1)
       {
               var paramsUrl = urlString.substring(urlEnd+typeQu.length);//paramsUrl=1&name=2
               var isEnd =  paramsUrl.indexOf('&');
               if(isEnd != -1)
            {
                    return paramsUrl.substring(0, isEnd);//得到info值为1
                }
                else
            {
                    return paramsUrl;//只有一个参数情况
                }
         }
         else 
             return null;//没有找到info=1
    }
    else
        return null;没有带参数的Url
}