upload.js

$files.forEach(function ($file) {
  console.log('Should request'); //This runs as many times as there are images
  var filePromise = $http.post('/api/images/upload').then(function (aws){  //This request runs only once
    console.log(aws) //This also runs as many times as there are images, but aws is same EVERY TIME.
    //Go on to upload file to S3
  });  
});