Front-end JS implements blob to Base64 bit and base64 bit to blob

**dataurl to blob**
function Dataurltoblob (dataurl) {
var arr = dataurl.split (', '), MIME = Arr[0].match (/:(. *); [1],
BSTR = Atob (arr[1]), n = bstr.length, U8arr = new Uint8array (n);
while (n--) {
U8arr[n] = bstr.charcodeat (n);
}
return new Blob ([U8arr], {type:mime});
}

**blob to dataurl**
function Blobtodataurl (BLOB, callback) {
var a = new FileReader ();
A.onload = function (e) {callback (e.target.result);}
A.readasdataurl (BLOB);
}

Test
var blob = Dataurltoblob (' data:text/plain;base64,ywfhywfhyq== ');
Blobtodataurl (BLOB, function (Dataurl) {
Console.log (Dataurl);
//});

Front-end JS implements blob to Base64 bit and base64 bit to blob