FileReader.onload

The FileReader.onload property contains a event handler executed when the load event is fired, when content read with readAsArrayBuffer, readAsBinaryString, readAsDataURL or readAsText is available.

Example

// Callback from a <input type="file" onchange="onChange(event)">
function onChange(event) {
  var file = event.target.files[0];
  var reader = new FileReader();
  reader.onload = function(event) {
    // The file's text will be printed here
    console.log(event.target.result)
  };

  reader.readAsText(file);
}