How to monitor the 'progress' of the upload?

use XMLHttpRequest, i listener 'progress', as  below:

``` javascript
var XHR = new XMLHttpRequest();
XHR.upload.addEventListener("progress", function(e) {
  if (e.lengthComputable) {　　　　　　
    var percentComplete = Math.round(e.position * 100 / e.total);
    console.log(percentComplete);
  }
}, false);
```

How do this with fetch ?
