dataURL to blob and blob to dataURL

convert.ts

//**dataURL to blob**
function dataURLtoBlob(dataurl: string) {
  const arr = dataurl.split(',')
  const fmt = arr[0]
  const b64 = arr[1]
  if (!fmt || !b64) throw new Error('invalid dataurl')

  const m = fmt.match(/:(.*?);/)
  if (!m) throw new Error('invalid dataurl')

  const mime = m[1]
  if (!mime) throw new Error('invalid dataurl')

  const bstr = atob(b64)
  let n = bstr.length
  const u8arr = new Uint8Array(n)
  while (n--) {
    u8arr[n] = bstr.charCodeAt(n)
  }
  return new Blob([u8arr], { type: mime })
}

//**blob to dataURL**
function blobToDataURL(blob: Blob, callback: (dataurl: string) => void) {
  const a = new FileReader()
  a.onload = (e) => {
    callback(e.target!.result as string)
  }
  a.readAsDataURL(blob)
}

//test:
const blob = dataURLtoBlob('data:text/plain;base64,YWFhYWFhYQ==');
blobToDataURL(blob, function(dataurl){
    console.log(dataurl)
})