前端js实现 blob转base64位 和 base64位转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);
//});