Convert a data URL, with base64 encoded data, to a Blob with binary data

base64-dataurl-to-blob.js

const mime = MIMEFromDataURI.getMIMEType(e.data); // using https://github.com/aautar/mime-from-data-uri
const dataB64 = e.data.split(',')[1];

const imageDataStr = window.atob(dataB64);
const imageDataBinaryArr = new Uint8Array(new ArrayBuffer(imageDataStr.length));

for (let i=0; i<imageDataStr.length; i++) {
    imageDataBinaryArr[i] = imageDataStr.charCodeAt(i);
}

const blob = new Blob([imageDataBinaryArr],  {type: mime});