convert base64 to blob object (from stackoverflow)

base64ToBlob.js

export const dataURItoBlob = (dataURI) => {
  // convert base64/URLEncoded data component to raw binary data held in a string
  let byteString
  if (dataURI.split(',')[0].indexOf('base64') >= 0) {
    byteString = atob(dataURI.split(',')[1])
  } else {
    byteString = unescape(dataURI.split(',')[1])
  }
  // separate out the mime component
  const mimeString = dataURI.split(',')[0].split(':')[1].split(';')[0]

  // write the bytes of the string to a typed array
  const ia = new Uint8Array(byteString.length)
  for (let i = 0; i < byteString.length; i++) {
    ia[i] = byteString.charCodeAt(i)
  }
  return new Blob([ia], {type:mimeString})
}