Decode base64 to binary string [duplicate]

/**
 * Function that converts a string into its binary representation
 * 
 * @see https://gist.github.com/eyecatchup/6742657
 * @author https://github.com/eyecatchup
 */
function stringToBinary(str, spaceSeparatedOctets) {
    function zeroPad(num) {
        return "00000000".slice(String(num).length) + num;
    }

    return str.replace(/[\s\S]/g, function(str) {
        str = zeroPad(str.charCodeAt().toString(2));
        return !1 == spaceSeparatedOctets ? str : str + " "
    });
};

let base64Str = 'AAAAAAAAAAAAAAAAAAAAAAAAAAEBAQEBAQEBAQEBAgICAwQEBwkMEBYcJTFAUGN8jqK3zNvo8/3/9+/f0ryijXlkTz0xJx0YEg8MCAYFBAMCAgIBAQEBAQEBAgICAgEBAQAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=='

document.getElementById("result").innerHTML = stringToBinary(base64Str, true);

<div id="result"></div>