用apply让javascript函数仅执行一次的代码

var obj = new Object();
obj.triggerOnce = function(fn) { //控制让函数只触发一次
return function() {
try {
fn.apply(this, arguments);
}
catch (e) {
var txt = "There was an error on this page.\n\n";
txt += "Error message: " + e.message + "\n\n";
txt += "Error name: " + e.name + "\n\n";
//alert(txt);//正式平台上可能需要注释掉该行
}
finally {
fn = null;
}
}
}

function showMsg(arg){
alert(arg);
}
var fn=obj.triggerOnce(showMsg);
fn(1);//只执行一次
fn(2);//没有调用fn

var urlStrs = location.search; //QueryString
var Request = {};
Request.Count = 0;
Request.Add = function(name, value) {
if (Request.hasOwnProperty(name) == false) {
Request.Count++; //如果不存在，计数添加1
}
Request[name] = value;
return true;
}
Request.QueryString = function(name) {//取对应的键值
var key = name.toString().toLocaleLowerCase(); //不区分大小写
var result = null;
try {
// if (Request.hasOwnProperty(key)) {
result = Request[key];
// }
}
catch (e) {
//alert(e.message);
}
return result;
}
Request.Init = function(urlQueryString) {
if (urlQueryString.indexOf("?") != -1) {
var url = urlQueryString.substr(1)
var strArr = url.split("&");
for (var i = 0; i < strArr.length; i++) {
var strChildArr = strArr[i].split("=");
var name = String(strChildArr[0]).toLowerCase();
var value = unescape(strChildArr[1]); //unescape解码
this.Add(name, value); //添加
}
}
}

//测试函数
function test() {
Request.Init(urlStrs); //初始化request
alert(Request.Count);
var name = "username";
var value = Request.QueryString(name);
alert(Request[name]);
alert(Request.QueryString(name));
name = "address"
alert(Request[name]);
alert(Request.QueryString(name));
name = "age";
alert(Request[name]);
alert(Request.QueryString(name));
}