FileReader Promise Helper

index.js

const readFile = (file) => {
  let reader = new global.FileReader();

  return new Promise((resolve, reject) => {
    reader.onload = (event) => {
      file.data = event.target. result;
      resolve(file);
    };

    reader.onerror = () => {
      return reject(this);
    };

    if (/^image/.test(file.type)) {
      reader.readAsDataURL(file);
    } else {
      reader.readAsText(file);
    }

  })

};