base64编码在python中，在javascript中解码

Question

A Python backend reads a binary file, base64 encodes it, inserts it into a JSON doc and sends it to a JavaScript frontend:

#Python
with open('some_binary_file', 'rb') as in_file:
    return base64.b64encode(in_file.read()).decode('utf-8')

The JavaScript frontend fetches the base64 encoded string from the JSON document and turns it into a binary blob:

#JavaScript
b64_string = response['b64_string'];
decoded_file = atob(b64_string);
blob = new Blob([decoded_file], {type: 'application/octet-stream'});

Unfortunately when downloading the blob the encoding seems to be wrong but I'm not sure where the problem is. Eg it is an Excel file that I can't open anymore. In the Python part I've tried different decoders ('ascii', 'latin1') but that doesn't make a difference. Is there a problem with my code?

Answer 1

I found the answer here . The problem was at the JavaScript side. It seems only applying atob to the base64 encoded string doesn't work for binary data. You'll have to convert that into a typed byte array. What I ended up doing (LiveScript):

byte_chars = atob base64_str
byte_numbers = [byte_chars.charCodeAt(index) for bc, index in byte_chars]
byte_array = new Uint8Array byte_numbers
blob = new Blob [byte_array], {type: 'application/octet-stream'}