anchor.diff:  <a id="ngStyle"></a>
   .l-main-section
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  -  ### NgStyle
  -
     ### NgStyle
   
     We can set inline styles dynamically, based on the state of the component.
  
positive.code:     要学习更多的*类似 index* 的值，例如`last`、`even`和`odd`，请参阅 [NgFor API 参考](../api/common/index/NgFor-directive.html)。
  
  :marked
    #### NgForTrackBy
  
    #### NgForTrackBy
  
    The `ngFor` directive has the potential to perform poorly, especially with large lists.
  
negative.code: :marked
    ### NgSwitch
  
    We bind to `NgSwitch` when we want to display *one* element tree (an element and its children)
    from a *set* of possible element trees, based on some condition.
    Angular puts only the *selected* element tree into the DOM.
  