FileReader not loading file properly using AngularJS

Question

I'm trying to load a csv file into AngularJS so I can do some manipulation on the contents. It is not quite working as I want it to. To test if it is loading properly, I am loading it into a textarea to view the contents.

When I load the file, it says it is loaded properly but the onload() event doesn't seem to be firing until I load a second CSV file, in which case the FIRST file is displayed in the textarea.

HTML:

<div>
  <input ng-model="csv"
            onchange="angular.element(this).scope().fileChanged()"
            type="file" accept=".csv" id="fileInput"/>
</div>
<br/>
<div>
  <textarea ng-model="csvFile" readonly="true" style="width:99%; height:500px" disabled></textarea>
</div>

JS:

$scope.fileChanged = function() {

  $scope.$apply(function() {
      var csvFileInput = document.getElementById('fileInput');
      var reader = new FileReader();
      var csvFile = csvFileInput.files[0];
      reader.onload = function(e) {
          $scope.csvFile = reader.result;
      };
      reader.readAsText(csvFile);
  });
};

And when I put this into JSFiddle, the file doesn't appear in the textarea at all. I'm new with JSFiddle so I don't know why that is happening.

Any help at all would be appreciated.

Answer 1

Reordering some lines of your code, hope the comments are explanatory enough

$scope.fileChanged = function() {

  // define reader
  var reader = new FileReader();

  // A handler for the load event (just defining it, not executing it right now)
  reader.onload = function(e) {
      $scope.$apply(function() {
          $scope.csvFile = reader.result;
      });
  };

  // get <input> element and the selected file 
  var csvFileInput = document.getElementById('fileInput');    
  var csvFile = csvFileInput.files[0];

  // use reader to read the selected file
  // when read operation is successfully finished the load event is triggered
  // and handled by our reader.onload function
  reader.readAsText(csvFile);
};

Reference: FileReader at MDN

Answer 2

This is just a minor improvement in HTML:

<input type="file" onchange="angular.element(this).scope().file_changed(this)"/>
<textarea cols="75" rows="15">{{ dataFile }}</textarea>

and controller:

.controller('MyCtrl', ['$scope', function($scope) {
    var vm = $scope;

    vm.file_changed = function(element){
        var dataFile = element.files[0];
        var reader = new FileReader();
        reader.onload = function(e){
            vm.$apply(function(){
                vm.dataFile = reader.result;
            });
        };
        reader.readAsText(dataFile);
    };
}]);

Ref