6月份小细节记录

1 关于typeof()的使用

var user;
if(typeof(user) == "undefined") {
alert("undefined");
}

var user = null;
if(typeof(user) == "undefined") {
alert("undefined");
} else {
alert("defined");
}

2 利用JS对象构造map

var map = {};
var key = "login";
map[key] = function(){
console.log("登录函数注册到map中");
}

alert(map[key]);

function TA_EventEmitter() {
this.callbacks = {};
};

TA_EventEmitter.prototype.on = function (event, fn) {
(this.callbacks[event] = this.callbacks[event] || [])
.push(fn);
return this;
};