Base64 to Blob file
Creating a blob from a base64 string
var b64Data = "base64 string here";
var byteCharacters = atob(b64Data);
var byteNumbers = new Array(byteCharacters.length);
for (var i = 0; i < byteCharacters.length; i++) {
byteNumbers[i] = byteCharacters.charCodeAt(i);
}
var byteArray = new Uint8Array(byteNumbers);
var blob = new Blob([byteArray], {type: "mimeType here"});
blob.name = "file name here";
blob.lastModifiedDate = "date";