Failed to decode base64 in javascript

Question

I receive an id_token as part of my current href. It is encoded in base64. I try to decode it using atob(extractedIdToken), but get the following error:

Failed to execute 'atob' on 'Window': The string to be decoded is not correctly encoded

When I copy and paste the extracted id_token in my code and go to an online decoding site, it decodes correctly. Do you have suggestion?

Can you include the string and reproduce error message at stacksnippets at Question? See stackoverflow.com/help/mcve — guest271314
I have solved my issue by writing the decoder in the backend and call it front end. See my answer at the end. — Donia Zaela
Then, the issue was also resolved in the front end. Just check my second answer below. — Donia Zaela

Israel Martins Israel Martins · Accepted Answer · 2017-11-10T15:44:15

I always use this to decode and encode in Base64, try it

var Base64 = {
    _keyStr: "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=",
    encode: function (e) {
        var t = "";
        var n, r, i, s, o, u, a;
        var f = 0;
        e = Base64._utf8_encode(e);
        while (f < e.length) {
            n = e.charCodeAt(f++);
            r = e.charCodeAt(f++);
            i = e.charCodeAt(f++);
            s = n >> 2;
            o = (n & 3) << 4 | r >> 4;
            u = (r & 15) << 2 | i >> 6;
            a = i & 63;
            if (isNaN(r)) {
                u = a = 64
            } else if (isNaN(i)) {
                a = 64
            }
            t = t + this._keyStr.charAt(s) + this._keyStr.charAt(o) + this._keyStr.charAt(u) + this._keyStr.charAt(a)
        }
        return t
    },
    decode: function (e) {
        var t = "";
        var n, r, i;
        var s, o, u, a;
        var f = 0;
        e = e.replace(/[^A-Za-z0-9+/=]/g, "");
        while (f < e.length) {
            s = this._keyStr.indexOf(e.charAt(f++));
            o = this._keyStr.indexOf(e.charAt(f++));
            u = this._keyStr.indexOf(e.charAt(f++));
            a = this._keyStr.indexOf(e.charAt(f++));
            n = s << 2 | o >> 4;
            r = (o & 15) << 4 | u >> 2;
            i = (u & 3) << 6 | a;
            t = t + String.fromCharCode(n);
            if (u != 64) {
                t = t + String.fromCharCode(r)
            }
            if (a != 64) {
                t = t + String.fromCharCode(i)
            }
        }
        t = Base64._utf8_decode(t);
        return t
    },
    _utf8_encode: function (e) {
        e = e.replace(/rn/g, "n");
        var t = "";
        for (var n = 0; n < e.length; n++) {
            var r = e.charCodeAt(n);
            if (r < 128) {
                t += String.fromCharCode(r)
            } else if (r > 127 && r < 2048) {
                t += String.fromCharCode(r >> 6 | 192);
                t += String.fromCharCode(r & 63 | 128)
            } else {
                t += String.fromCharCode(r >> 12 | 224);
                t += String.fromCharCode(r >> 6 & 63 | 128);
                t += String.fromCharCode(r & 63 | 128)
            }
        }
        return t
    },
    _utf8_decode: function (e) {
        var t = "";
        var n = 0;
        var r = c1 = c2 = 0;
        while (n < e.length) {
            r = e.charCodeAt(n);
            if (r < 128) {
                t += String.fromCharCode(r);
                n++
            } else if (r > 191 && r < 224) {
                c2 = e.charCodeAt(n + 1);
                t += String.fromCharCode((r & 31) << 6 | c2 & 63);
                n += 2
            } else {
                c2 = e.charCodeAt(n + 1);
                c3 = e.charCodeAt(n + 2);
                t += String.fromCharCode((r & 15) << 12 | (c2 & 63) << 6 | c3 & 63);
                n += 3
            }
        }
        return t
    }
};

Failed to decode base64 in javascript

3 Answers