详解JavaScript中的客户端消息框架设计原理

var observer = {
 listen : function() {
  console.log("Yay for more cliché examples...");
 }
};
var elem = document.getElementById("cliche");
elem.addEventListener("click", observer.listen);

// It's fun to be naive!
var mediator = {
 _subs: {},
 // a real subscribe would at least check to make sure the
 // same callback instance wasn't registered 2x.
 // Sheesh, where did they find this guy?!
 subscribe: function(topic, callback) {
  this._subs[topic] = this._subs[topic] || [];
  this._subs[topic].push(callback);
 },
 // lolwut? No ability to pass function context? :-)
 publish : function(topic, data) {
  var subs = this._subs[topic] || [];
  subs.forEach(function(cb) {
   cb(data);
  });
 }
}
var FatherTime = function(med) { this.mediator = med; };
FatherTime.prototype.wakeyWakey = function() {
 this.mediator.publish("alarm.clock", {
  time: "06:00 AM",
  canSnooze: "heck-no-get-up-lazy-bum"
 });
}
var Developer = function(mediator) {
 this.mediator = mediator;
 this.mediator.subscribe("alarm.clock", this.pleaseGodNo);
};
Developer.prototype.pleaseGodNo = function(data) {
 alert("ZOMG, it's " + data.time + ". Please just make it stop.");
}
var fatherTime = new FatherTime(mediator);
var developer = new Developer(mediator);
fatherTime.wakeyWakey();

var SomeModel = Backbone.Model.extend({
 initialize: function() {
  this.on("change:superImportantField", function(model, value) {
   postal.publish({
    channel : "someChannel",
    topic : "omg.super.important.field.changed",
    data : {
    muyImportante: value,
    otherFoo: "otherBar"
    }
   });
  });
 }
});

// the logic to wire up publications and subscriptions
// exists in our custom MsgBackboneView constructor
var SomeView = MsgBackboneView.extend({
 
 className : "i-am-classy",
 
 // bridging local events triggered by this view
 publications: {
 // This is the more common 'shorthand' syntax
 // The key name is the name of the event. The
 // value is "channel topic" in postal. So this
 // means the bridgeTooFar event will get
 // published to postal on the "comm" channel
 // using a topic of "thats.far.enough". By default
 // the 1st argument passed to the event callback
 // will become the message payload.
 bridgeTooFar : "comm thats.far.enough",
 
 // However, the longhand approach works like this:
 // The key is still the event name that will be bridged.
 // The value is an object that provides a channel name,
 // a topic (which can be a string or a function returning
 // a string), and an optional data function that returns
 // the object that should be the message payload.
 bridgeBurned: {
  channel : "comm",
  topic : "match.lit",
  data : function() {
   return { id: this.get("id"), foo: 'bar' };
  }
 },
 
 // This is how we subscribe to the bus and invoke
 // local methods to handle incoming messages
 subscriptions: {
  // The key is the name of the method to invoke.
  // The value is the "channel topic" to subscribe to.
  // So this will subscribe to the "hotChannel" channel
  // with a topic binding of "start.burning.*", and any
  // message arriving gets routed to the "burnItWithFire"
  // method on the view.
  burnItWithFire : "hotChannel start.burning.*"
 },
 
 burnItWithFire: function(data, envelope) {
  // do stuff with message data and/or envelope
 }
 
 // other wire-up, etc.
});

// using the 'monopost' add-on for monologue/postal:
// assuming we have a worker instance that has monologue
// methods on its prototype chain, etc. The keys are event
// topic bindings to match local events to, and if a match is
// found, it gets published to the channel specified in the
// value (using the same topic value)
worker.goPostal({
 "match.stuff.like.#" : "ThisChannelYo",
 "secret.sauce.*" : "SeeecretChannel",
 "another.*.topic" : "YayMoarChannelsChannel"
});

// 0-n args
this.trigger("someGuyBlogged", "Jim", "Cowart", "JavaScript");
// envelope style
this.emit("someGuyBlogged", {
 firstName: "Jim",
 lastName: "Cowart",
 category: "JavaScript"
});
/*
 In an emitter like monologue.js, the emit call above
 would actually publish an envelope that looked similar
 to this:
 {
  topic: "someGuyBlogged",
  timeStamp: "2013-02-05T04:54:59.209Z",
  data : {
   firstName: "Jim",
   lastName: "Cowart",
   category: "JavaScript"
  }
 }
*/

// 最开始是这样的
this.trigger("someEvent", "a string!", 99);
// 有一天， 它变得包含了一切
this.trigger("someEvent", "string", 99, { sky: "blue" }, [1,2,3,4], true, 0);
// 可是等等——第4和第5个参数是可选的，因此也可能传的是：
this.trigger("someEvent", "string", 99, [1,2,3,4], true, 0);
// 噢，你还检查第5个参数的真/假吗?
// 哎呦！现在是早先的参数了……
this.trigger("someEvent", "string", 99, true, 0);