Javascript观察者模式

var pubsub = {};
(function (q) {

var topics = {}, // 回调函数存放的数组
subUid = -1;
// 发布方法
q.publish = function (topic, args) {

if (!topics[topic]) {
return false;
}

setTimeout(function () {
var subscribers = topics[topic],
len = subscribers ? subscribers.length : 0;

while (len--) {
subscribers[len].func(topic, args);
}
}, 0);

return true;

};
//订阅方法
q.subscribe = function (topic, func) {

if (!topics[topic]) {
topics[topic] = [];
}

var token = (++subUid).toString();
topics[topic].push({
token: token,
func: func
});
return token;
};
//退订方法
q.unsubscribe = function (token) {
for (var m in topics) {
if (topics[m]) {
for (var i = 0, j = topics[m].length; i < j; i++) {
if (topics[m][i].token === token) {
topics[m].splice(i, 1);
return token;
}
}
}
}
return false;
};
} (pubsub));
将订阅者放在了字典值，发布时通过控制键来控制订阅者。
----------------------------------------------------------------
function Observer() {
this.fns = [];
}
Observer.prototype = {
subscribe: function (fn) {
this.fns.push(fn);
},
unsubscribe: function (fn) {
this.fns = this.fns.filter(
function (el) {
if (el !== fn) {
return el;
}
}
);
},
update: function (o, thisObj) {
var scope = thisObj || window;
this.fns.forEach(
function (el) {
el.call(scope, o);
}
);
}
};

//测试
var o = new Observer;
var f1 = function (data) {
console.log('Robbin: ' + data + ', 赶紧干活了！');
};

var f2 = function (data) {
console.log('Randall: ' + data + ', 找他加点工资去！');
};

o.subscribe(f1);
o.subscribe(f2);

o.update("Tom回来了！")

//退订f1
o.unsubscribe(f1);
//再来验证
o.update("Tom回来了！");

和上相同， 把所有的订阅者放在了数组里面了。
---------------------------------------------------------------------
//通用代码
var observer = {
//订阅
addSubscriber: function (callback) {
this.subscribers[this.subscribers.length] = callback;
},
//退订
removeSubscriber: function (callback) {
for (var i = 0; i < this.subscribers.length; i++) {
if (this.subscribers[i] === callback) {
delete (this.subscribers[i]);
}
}
},
//发布
publish: function (what) {
for (var i = 0; i < this.subscribers.length; i++) {
if (typeof this.subscribers[i] === 'function') {
this.subscribers[i](what);
}
}
},
// 将对象o具有观察者功能  [ 将 o 对象赋予此对象的功能 ]
make: function (o) {
for (var i in this) {
o[i] = this[i];
o.subscribers = [];
}
}
};

var blogger = {
recommend: function (id) {
var msg = 'dudu 推荐了的帖子:' + id;
this.publish(msg);
}
};

var user = {
vote: function (id) {
var msg = '有人投票了!ID=' + id;
this.publish(msg);
}
};

observer.make(blogger);
observer.make(user);

var tom = {
read: function (what) {
console.log('Tom看到了如下信息：' + what)
}
};

var mm = {
show: function (what) {
console.log('mm看到了如下信息：' + what)
}
};
// 订阅
blogger.addSubscriber(tom.read);
blogger.addSubscriber(mm.show);
blogger.recommend(123); //调用发布

//退订
blogger.removeSubscriber(mm.show);
blogger.recommend(456); //调用发布

//另外一个对象的订阅
user.addSubscriber(mm.show);
user.vote(789); //调用发布

比较重要的是上面那个make函数 ，将对象扩充。赋予了参数对象职能。
-----------------------------------------------------------
jQuery 版本：
(function ($) {

var o = $({});

$.subscribe = function () {
o.on.apply(o, arguments);
};

$.unsubscribe = function () {
o.off.apply(o, arguments);
};

$.publish = function () {
o.trigger.apply(o, arguments);
};

} (jQuery));
调用方法比上面3个版本都简单：

//回调函数
function handle(e, a, b, c) {
// `e`是事件对象，不需要关注
console.log(a + b + c);
};

//订阅
$.subscribe("/some/topic", handle);
//发布
$.publish("/some/topic", ["a", "b", "c"]); // 输出abc

$.unsubscribe("/some/topic", handle); // 退订

//订阅
$.subscribe("/some/topic", function (e, a, b, c) {
console.log(a + b + c);
});

$.publish("/some/topic", ["a", "b", "c"]); // 输出abc

//退订（退订使用的是/some/topic名称，而不是回调函数哦，和版本一的例子不一样
$.unsubscribe("/some/topic");