base64ToFile.ts

const base64ToFile (base64Data: string, filename: string, mimeType: string): File => {
  const binaryString = atob(base64Data)
  const arrayBuffer = new ArrayBuffer(binaryString.length)
  const uint8Array = new Uint8Array(arrayBuffer)
  for (let i = 0; i < binaryString.length; i++) {
    uint8Array[i] = binaryString.charCodeAt(i)
  }

  const blob = new Blob([uint8Array], { type: mimeType })
  return new File([blob], filename, { type: mimeType })
}

// base64ToFile(<BASE_64>, 'banner.png', 'image/png')