promises-notify.js

function uploadFile(data) {
  // we can send notification one or more time as following:
  defer.notify(percentageUploaded);
  
  // returns promise
}

uploadFile()
  .then(function() {
    // fine
  }, function() {
    // error
  }, function(percenatage) {
    // get updates before resolving or rejecting the promise
    console.log('Uploaded ' + percenatage + '% ...');
  });