toBase64.js

function getArrayBuffer(file) {
  return new Promise((resolve, reject) => {
    const reader = new FileReader();
    reader.addEventListener('load', () => {
      resolve(reader.result);
    });
    
    reader.addEventListener('error', () => {
      reject();
    });

    reader.readAsDataURL(file);
  });
}

export default async function handleUpload(file, callback) {
  try {
    const dataUrl = await getArrayBuffer(file);
    callback(dataUrl);
  } catch (error) {
    throw new Error('Upload error');
  }
}