anchor.diff:  
     The `Content-Type` header allows us to inform the server that the body will represent JSON.
     
  -  我们通过这个`Content-Type`头告诉服务器，body是JSON格式的。
  +  我们通过`Content-Type`头告诉服务器，body是JSON格式的。
   
   +ifDocsFor('ts')
     :marked
  
positive.code: 
  block promises
    h2#promises Fall back to Promises
    h2#promises 退化为承诺(Promise)
    :marked
      Although the Angular `http` client API returns an `Observable<Response>` we can turn it into a 
      [Promise<Response>](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise) if we prefer.
  
negative.code:   <a id="query-parameters"></a>
    :marked
      ### Search parameters
  
      ### 搜索参数
      
      The [Wikipedia 'opensearch' API](https://www.mediawiki.org/wiki/API:Opensearch)
      expects four parameters (key/value pairs) to arrive in the request URL's query string.
      The keys are `search`, `action`, `format`, and `callback`.
  