Using Javascript's atob to decode base64 doesn't properly decode utf-8 strings

Question

I\'m using the Javascript window.atob() function to decode a base64-encoded string (specifically the base64-encoded content from the GitHub API). Problem is I\'

Answer 1

Decoding base64 to UTF8 String

Below is current most voted answer by @brandonscript

function b64DecodeUnicode(str) {
    // Going backwards: from bytestream, to percent-encoding, to original string.
    return decodeURIComponent(atob(str).split('').map(function(c) {
        return '%' + ('00' + c.charCodeAt(0).toString(16)).slice(-2);
    }).join(''));
}

Above code can work, but it's very slow. If your input is a very large base64 string, for example 30,000 chars for a base64 html document. It will need lots of computation.

Here is my answer, use built-in TextDecoder, nearly 10x faster than above code for large input.

function decodeBase64(base64) {
    const text = atob(base64);
    const length = text.length;
    const bytes = new Uint8Array(length);
    for (let i = 0; i < length; i++) {
        bytes[i] = text.charCodeAt(i);
    }
    const decoder = new TextDecoder(); // default is utf-8
    return decoder.decode(bytes);
}