JavaScript - convert Blob to Base64 (web browser API)

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
const toBase64 = async (blob) => {
    return new Promise((resolve, reject) => {
        const reader = new FileReader();
        reader.onload = function() {
            var url = reader.result;
            if (url) {
                const index = url.indexOf('base64,');
                if (index === -1) {
                    reject('Base64 data is not available.');
                } else {
                    resolve(url.substring(index + 7));
                }
            } else {
                reject('Base64 data is not available.');
            }
        };
        reader.onerror = function() {
            reject('Incorrect blob object.');
        };
        reader.readAsDataURL(blob);
    });
};



// Usage example (use in async context):

const blob = ...;  // Note: File class is also Blob class (File extends Blob) 
const base64 = await toBase64(blob);



// See also:
//
//     1. https://dirask.com/snippets/JavaScript-convert-File-to-Base64-web-browser-API-1RN8N1
//     2. https://dirask.com/snippets/JavaScript-convert-base64-to-Blob-j8dYrj