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Copy path44_支持先发布再订阅、并提供命名空间的观察者模式.html
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44_支持先发布再订阅、并提供命名空间的观察者模式.html
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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
</head>
<body>
<pre>
有时，需要先发布，再订阅。如42中的登录，获取登录信息可能很快，但其他模块可能加载的很慢，就会造成已经发布了登录成功的消息，但其他模块还没有订阅的错误。
所以需要让观察者模式支持先缓存要发布的消息，等到有模块订阅消息的时候再正式发布消息。
另外，Event对象中只存在一个clientList，当订阅多了，就可能出现命名冲突的问题。所以还需要支持创建命名空间。
</pre>
<script>
var Event = (function() {
var global = this,
Event, _default = "default";
Event = function() {
var _listen, _trigger, _remove, _slice = Array.prototype.slice,
_shift = Array.prototype.shift,
_unshift = Array.prototype.unshift,
namespaceCache = {},
_create, find, each = function(ary, fn) {
var ret;
for (var i = 0, l = ary.length; i < l; i++) {
var n = ary[i];
ret = fn.call(n, i, n);
}
return ret;
};
_listen = function(key, fn, cache) {
if (!cache[key]) {
cache[key] = [];
}
cache[key].push(fn);
};
_remove = function(key, cache, fn) {
if (cache[key]) {
if (fn) {
for (var i = cache[key].length; i >= 0; i--) {
if (cache[key][i] === fn) {
cache[key].splice(i, 1);
}
}
} else {
cache[key] = {};
}
}
};
_trigger = function() {
var cache = _shift.call(arguments),
key = _shift.call(arguments),
args = arguments,
_self = this,
ret, stack = cache[key];
if (!stack || !stack.length) {
return;
}
return each(stack, function() {
return this.apply(_self, args);
});
};
_create = function(namespace) {
var namespace = namespace || _default;
var cache = {},
offlineStack = [], // 离线事件
ret = {
listen: function(key, fn, last) {
_listen(key, fn, cache);
if (offlineStack === null) {
return;
}
if (last === "last") {
offlineStack.length && offlineStack.pop()();
} else {
each(offlineStack, function() {
this();
});
}
offlineStack = null;
},
one: function(key, fn, last) {
_remove(key, cache);
this.listen(key, fn, last);
},
remove: function(key, fn) {
_remove(key, cache, fn);
},
trigger: function() {
var fn, args, _self = this;
_unshift.call(arguments, cache);
args = arguments;
fn = function() {
return _trigger.apply(_self, args);
};
if (offlineStack) {
return offlineStack.push(fn);
}
return fn();
}
};
return namespace ?
(namespaceCache[namespace] ? namespaceCache[namespace] :
namespaceCache[namespace] = ret) : ret;
};
return {
create: _create,
one: function(key, fn, last) {
var event = this.create();
event.one(key, fn, last);
},
remove: function(key, fn) {
var event = this.create();
event.remove(key, fn);
},
listen: function(key, fn, last) {
var event = this.create();
event.listen(key, fn, last);
},
trigger: function() {
var event = this.create();
event.trigger.apply(this, arguments);
}
};
}();
return Event;
})();
/************** 先发布后订阅 ********************/
Event.trigger('click', 1);
Event.listen('click', function(a) {
console.log(a); // 输出：1
});
/************** 使用命名空间 ********************/
Event.create('namespace1').listen('click', function(a) {
console.log(a); // 输出：1
});
Event.create('namespace1').trigger('click', 1);
Event.create('namespace2').listen('click', function(a) {
console.log(a); // 输出：2
});
Event.create('namespace2').trigger('click', 2);
</script>
</body>
</html>