anchor.diff:    it calls the lifecycle hook methods in the following sequence at specific moments:
     
     当Angular使用构造函数新建一个组件或指令后，就会按下面的顺序在特定时刻调用这些生命周期钩子方法：  
  +  
   table(width="100%")
     col(width="20%")
     col(width="80%")
  
positive.code:   Angular创建它，渲染它，创建并渲染它的子组件，在它被绑定的属性发生变化时检查它，并在它从DOM中被移除前销毁它。
  
    Angular offers **lifecycle hooks**
    that provide visibility into these key moments and the ability to act when they occur.
    
    Angular提供了**生命周期钩子**，把这些关键时刻暴露出来，赋予我们在它们发生时采取行动的能力。
  
    A directive has the same set of lifecycle hooks, minus the hooks that are specific to component content and views.
    
  
negative.code:   
    Directive and component instances have a lifecycle
    as Angular creates, updates, and destroys them.
    Developers can tap into key moments in that lifecycle by implementing
    one or more of the *Lifecycle Hook* interfaces in the Angular `core` library.
    
    指令和组件的实例有一个生命周期：新建、更新和销毁。
    通过实现一个或多个Angular `core`库里定义的*生命周期钩子*接口，开发者可以介入该生命周期中的这些关键时刻。
    
    Each interface has a single hook method whose name is the interface name prefixed with `ng`.
  