识别 URL 后面参数

function getQueryString(name) { 
    var reg = new RegExp("(^|&)" + name + "=([^&]*)(&|$)", "i");  
    var r = window.location.search.substr(1).match(reg);  //获取url中"?"符后的字符串并正则匹配
    var context = "";  
    if (r != null)  
         context = r[2];  
    reg = null;  
    r = null;  
    return context == null || context == "" || context == "undefined" ? "" : context;  
}

另外 switch case 判定不同参数值，需把数字改成字符串，否则失效