anchor.diff:    ```
     <div [ng-style]="setStyles()">This div is italic, normal weight, and larger</div>
     ```
  +
     <a id="ng-if"></a>
     ### NgIf
     We can add an element sub-tree (an element and its children) to the DOM  by binding an `NgIf` directive to a truthy expression; binding to a falsey expression removes the element sub-tree from the DOM.
  
positive.code:   When `NgIf` is `false`, Angular physically removes the element sub-tree from the DOM. It destroys components in the sub-tree along with their state which may free up substantial resources resulting in better performance for the user.
  
    The show/hide technique is probably fine for small element trees. We should be wary when hiding large trees; `NgIf` may be the safer choice. Always measure before leaping to conclusions.
    <a id="ng-switch"></a>
    NgSwitch
    We bind to `NgSwitch` when we want to insert one element sub-tree (an element and its children) into the DOM from a set of alternative sub-trees.
  
    Here’s an example:
  
negative.code:   ```
    <div [ng-class]="setClasses()">This div is saveable and special</div>
    ```
  
    <a id="ng-style"></a>
    ### NgStyle
    We may set inline styles dynamically based on the state of the component.
  