title: react native upload video with fetch blob and image picker
body: <p>get path video file with react native image picker:</p>
  
  <pre><code>{path: "/storage/emulated/0/DCIM/Camera/VID_20171123_122202.mp4", uri: 
  "content://media/external/video/media/50"}
  </code></pre>
  
  <p>send file with react native fetch blob with wrap:</p>
  
  <pre class="lang-js prettyprint-override"><code>     let url=CounterStore.base_url+'upload/video?
      &amp;api_token='+CounterStore.api_token;
          RNFetchBlob.fetch('POST', url, {
              'Content-Type' : 'multipart/form-data',
          }, [
  
      // part file from storage
      { name : 'avatar-foo', filename : 'avatar-foo.png', 
      type:'image/foo', data: RNFetchBlob.wrap(this.state.data.path)},
      // elements without property `filename` will be sent as plain text
     { name : 'name', data : 'user'},
      { name : 'info', data : JSON.stringify({
       mail : 'example@example.com',
       tel : '12345678'
              })},
          ]).then((resp) =&gt; {
              console.log(resp)
          }).catch((err) =&gt; {
              console.log(err)
          })
  </code></pre>
  
  <p>not return video data in server:</p>
  
  <pre><code>`FetchBlobResponse {data: "{"name":"user","info":"{\"mail\":\"example@example…p8njbIxpJGLDA8fte6QEgbWQOVU3Vhf","avatar-foo":{}}", taskId: "8f`vfiutibvhss2jt8eh62", type: "utf8", respInfo: {…}, info: ƒ, …}
  </code></pre>
  
  <p>avator-foo is empty.why?</p>