anchor.diff:      tells Angular how to link the reference variable to the directive.
       We set `name` to `ngModel` because the `ngModel` directive's `exportAs` property happens to be "ngModel".
   
  -    为什么是“ngModel”？
  +    为什么是 “ngModel”？
       指令的 [exportAs](../api/core/index/DirectiveMetadata-class.html#!#exportAs) 属性告诉 Angular 如何链接模板引用变量到指令。
  -    这里把`name`设置为`ngModel`是因为`ngModel`指令的`exportAs`属性设置成了“ngModel”。
  +    这里把`name`设置为`ngModel`是因为`ngModel`指令的`exportAs`属性设置成了 “ngModel”。
   
       Now we can control visibility of the "name" error message by binding properties of the `name` control to the message `<div>` element's `hidden` property.
   
  
positive.code:   1. We threw in a `diagnostic` property at the end to return a JSON representation of our model.
    It'll help us see what we're doing during our development; we've left ourselves a cleanup note to discard it later.
  
       在最后增加`diagnostic`属性，它返回这个模型的JSON形式。
    在开发过程中，它用于调试，最后清理时会丢弃它。
  
    ### Why the separate template file?
  
negative.code:   Here we created a variable called `name` and gave it the value "ngModel".
  
    模板引用变量可以访问模板中输入框的 Angular 控件。
    这里，创建了名叫`name`的变量，并且赋值为 "ngModel"。
  
  .l-sub-section
    :marked
  