微信小程序跨页面通信解决思路

小鱼儿 2022-05-20 02:21 257阅读 0赞

宏观上，微信小程序是由一个个 Page 组成的。有时候我们会遇到一些业务存在耦合的 Page，一个 Page 里某个状态改变后，相关 Page 的状态需要进行更新。而在小程序里，每个 Page 都是一个模块，有着独立的作用域，因此 Page 间需要有一种通信策略。

想象一个业务场景，用户首先进入订单列表页。然后点击其中一个订单，进入到订单详情页。当用户在订单详情页对订单进行操作，例如支付、确认收货等时，该订单的状态就会发生改变。此时需要对上一级的订单列表页中该订单的状态进行更新：

![example][]

要想更新订单列表页的视图层，就需要调用该 Page 对象的 `setData` 方法。这里为大家列举三种比较常用的方案：

## 设置标志位 ##

最简单的方法，在订单详情页对订单的操作成功回调中，把一些标志位设置为 true，并设置好参数（标志位和参数可以存在 localStorage 或挂在全局 App 对象下）。然后每次在订单列表页的 onShow 生命周期中，根据这些标志位去判断是否进行更新、更新的参数是什么。

这种处理在业务逻辑比较简单、页面间的耦合度很小时还能凑合，一旦逻辑复杂起来，就需要写很多冗余的代码，并且维护成本会非常高。

流程图：

![planA][]

## 利用页面栈获取 Page 对象 ##

如果订单详情页里能拿到订单列表页的 Page 对象，就能去调用它的 setData 方法。小程序提供了一个方法 `getCurrentPages`，执行它可以得到当前页面栈的实例，然后再根据页面进栈的顺序我们就能拿到订单列表页的 Page 对象。

然而这种做法的缺点还是耦合度太大，过度依赖页面进栈顺序。一旦在以后的产品迭代中页面顺序发生变化，将很难去维护。

流程图：

![planB][]

上述两种方法都存在着耦合度大、维护困难的问题，而利用发布／订阅模式能很好的实现解耦，下面我们先来了解一下这种设计模式。

## 发布／订阅模式（最优方案） ##

发布／订阅模式由一个发布者、多个订阅者以及一个调度中心所组成。订阅者们先在调度中心订阅某一事件并注册相应的回调函数，当某一时刻发布者发布了一个事件，调度中心会取出订阅了该事件的订阅者们所注册的回调函数来执行。

![publish / subscribe][publish _ subscribe]

在发布／订阅模式中，订阅者和发布者并不需要关心对方的状态，订阅者只管订阅事件并注册回调、发布者只管发布事件，其余一切交给调度中心来调度，从而能实现解耦。

在 app 跨页面通信这个问题上，iOS 端的 Notification Center、安卓端的 EventBus，也是通过这样一种设计模式去解决的，不过微信小程序内部并没有提供这种事件通知机制，所以我们需要手动去实现一个。

我们首先要实现一个 Event 类，它应该含有一个收集回调函数的对象，和提供三个基础方法：on（订阅）、 emit（发布）、 off（注销）。

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    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(142,144,140);">// event.js</span> 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"></div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"><span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">class</span> <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(62,153,159);">Event</span> </span>{ 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(142,144,140);">/**</span> 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      * on 方法把订阅者所想要订阅的事件及相应的回调函数记录在 Event 对象的 _cbs 属性中 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      */ 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      on (event, fn) { 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">if</span> ( 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">typeof</span> fn != 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(113,140,0);">"function"</span>) { 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(245,135,31);">console</span>.error( 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(113,140,0);">'fn must be a function'</span>) 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">return</span> 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      } 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">this</span>._cbs = 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">this</span>._cbs || {} 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      ;( 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">this</span>._cbs[event] = 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">this</span>._cbs[event] || []).push(fn) 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      } 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"></div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"></div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(142,144,140);">/**</span> 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      * emit 方法接受一个事件名称参数，在 Event 对象的 _cbs 属性中取出对应的数组，并逐个执行里面的回调函数 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      */ 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      emit (event) { 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">this</span>._cbs = 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">this</span>._cbs || {} 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">var</span> callbacks = 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">this</span>._cbs[event], args 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"></div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">if</span> (callbacks) { 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      callbacks = callbacks.slice( 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(113,140,0);">0</span>) 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      args = [].slice.call( 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(245,135,31);">arguments</span>, 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(113,140,0);">1</span>) 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">for</span> ( 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">var</span> i = 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(113,140,0);">0</span>, len = callbacks.length; i &lt; len; i++) { 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      callbacks[i].apply( 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(245,135,31);">null</span>, args) 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      } 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      } 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      } 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"></div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"></div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"></div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(142,144,140);">/**</span> 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      * off 方法接受事件名称和当初注册的回调函数作参数，在 Event 对象的 _cbs 属性中删除对应的回调函数。 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      */ 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      off (event, fn) { 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">this</span>._cbs = 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">this</span>._cbs || {} 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"></div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(142,144,140);">// all</span> 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">if</span> (! 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(245,135,31);">arguments</span>.length) { 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">this</span>._cbs = {} 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">return</span> 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      } 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"></div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">var</span> callbacks = 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">this</span>._cbs[event] 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">if</span> (!callbacks) 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">return</span> 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"></div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(142,144,140);">// remove all handlers</span> 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">if</span> ( 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(245,135,31);">arguments</span>.length === 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(113,140,0);">1</span>) { 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">delete</span> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">this</span>._cbs[event] 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">return</span> 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      } 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"></div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(142,144,140);">// remove specific handler</span> 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">var</span> cb 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">for</span> ( 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">var</span> i = 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(113,140,0);">0</span>, len = callbacks.length; i &lt; len; i++) { 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      cb = callbacks[i] 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">if</span> (cb === fn || cb.fn === fn) { 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      callbacks.splice(i, 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(113,140,0);">1</span>) 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">break</span> 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      } 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      } 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">return</span> 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      } 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      } 
    </div></td> 
  </tr> 
 </tbody> 
</table>

### 具体调用方法 ###

App 是小程序的实例，在每个 Page 里都能通过执行 `getApp` 函数获取到它。我们可以把 Event 类的实例挂载在 App 中，方便每个 Page 去调用。

订单列表页在 onLoad 生命周期中订阅 “afterPaySuccess” 事件。

在订单详情页支付成功的回调中，发布 “afterPaySuccess” 事件,同时带上订单 id 参数。

所有 Page 的 onUnload 生命周期，必须注销掉之前订阅的事件。注销方法 off 的调用姿势有三种，不过还是建议注销当前 Page 所订阅的事件，而不是注销所有的。

到此就结束了吗？还没有，按照我们的订阅、注销写法，在注销指定回调函数的时候，其实是永远注销不了的。

### 完善off方法 ###

为了让每个回调函数被调用时的 this 都指向对应的 Page 对象，必须在订阅时对回调函数绑定当前的上下文对象。

相当于

正因为 bind 方法会返回这样一个匿名函数，然后这个匿名函数会被加入到回调数组中。因此我们注销指定回调函数的时候，在回调数组中是找不到它的，也就永远无法注销。

为了保持我们原来的 emit 调用方式，我想过直接把 Function.prototype.bind 改写：

然后再稍微修改一下 off 方法里的判断条件

在浏览器环境这种做法是可行的，但是在小程序侧则是失败的。因为我们定义的这些 function 在小程序里并不是 Function 的实例，那无论我怎样修改 Function 的 prototype 属性，function 并不会继承到。原因是小程序把 Function 给改写了：

#### 优化方案 ####

在小程序环境中是不能偷懒了，需要把之前的代码改写一下。要把 Page 对象也传给调度中心保存起来，作为回调函数调用时的上下文对象。

代码：

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   <td style="font-style:inherit;font-family:inherit;font-size:12px;vertical-align:baseline;color:rgb(51,51,51);"><pre style="border:none;font-style:inherit;font-family:'Input Mono', 'PT Mono', Consolas, Monaco, Menlo, monospace;vertical-align:baseline;background:rgb(247,247,247);color:rgb(77,77,76);line-height:1.6;"></pre> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(142,144,140);">//event.js</span> 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"></div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"><span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">class</span> <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(62,153,159);">Event</span> </span>{ 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"></div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      on (event, fn, ctx) { 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">if</span> ( 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">typeof</span> fn != 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(113,140,0);">"function"</span>) { 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(245,135,31);">console</span>.error( 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(113,140,0);">'fn must be a function'</span>) 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">return</span> 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      } 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">this</span>._stores = 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">this</span>._stores || {} 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      ;( 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">this</span>._stores[event] = 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">this</span>._stores[event] || []).push({ 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">cb</span>: fn, 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">ctx</span>: ctx}) 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      } 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"></div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      emit (event) { 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">this</span>._stores = 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">this</span>._stores || {} 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">var</span> store = 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">this</span>._stores[event], args 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"></div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">if</span> (store) { 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      store = store.slice( 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(113,140,0);">0</span>) 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      args = [].slice.call( 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(245,135,31);">arguments</span>, 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(113,140,0);">1</span>) 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">for</span> ( 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">var</span> i = 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(113,140,0);">0</span>, len = store.length; i &lt; len; i++) { 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      store[i].cb.apply(store[i].ctx, args) 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      } 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      } 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      } 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"></div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      off (event, fn) { 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">this</span>._stores = 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">this</span>._stores || {} 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"></div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(142,144,140);">// all</span> 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">if</span> (! 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(245,135,31);">arguments</span>.length) { 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">this</span>._stores = {} 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">return</span> 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      } 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"></div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(142,144,140);">// specific event</span> 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">var</span> store = 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">this</span>._stores[event] 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">if</span> (!store) 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">return</span> 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"></div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(142,144,140);">// remove all handlers</span> 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">if</span> ( 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(245,135,31);">arguments</span>.length === 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(113,140,0);">1</span>) { 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">delete</span> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">this</span>._stores[event] 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">return</span> 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      } 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"></div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(142,144,140);">// remove specific handler</span> 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">var</span> cb 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">for</span> ( 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">var</span> i = 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(113,140,0);">0</span>, len = store.length; i &lt; len; i++) { 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      cb = store[i].cb 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">if</span> (cb === fn) { 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      store.splice(i, 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(113,140,0);">1</span>) 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">break</span> 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      } 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      } 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;"> 
     <span style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;color:rgb(137,89,168);">return</span> 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      } 
    </div> 
    <div style="border:0px;font-style:inherit;font-family:inherit;vertical-align:baseline;">
      } 
    </div></td> 
  </tr> 
 </tbody> 
</table>

调用方法也需要改一下，不需要使用 bind 方法了，只需传入 Page 对象：

[example]: https://misc.aotu.io/Chen-jj/event-example.png
[planA]: https://misc.aotu.io/Chen-jj/event-planA.png
[planB]: https://misc.aotu.io/Chen-jj/event-planB.png
[publish _ subscribe]: https://misc.aotu.io/Chen-jj/publish.png