Javascript Promises with FileReader()

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We modified midos answer to get it to work the following:

function readFile(file){
  return new Promise((resolve, reject) => {
    var fr = new FileReader();  
    fr.onload = () => {
      resolve(fr.result )
    };
    fr.onerror = reject;
    fr.readAsText(file.blob);
  });
}

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