atob.js

/**
 * The code was extracted from:
 * https://github.com/davidchambers/Base64.js
 */

var chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";

function InvalidCharacterError(message) {
    this.message = message;
}

InvalidCharacterError.prototype = new Error();
InvalidCharacterError.prototype.name = "InvalidCharacterError";

function polyfill(input) {
    var str = String(input).replace(/=+$/, "");
    if (str.length % 4 == 1) {
        throw new InvalidCharacterError(
            "'atob' failed: The string to be decoded is not correctly encoded."
        );
    }
    for (
        // initialize result and counters
        var bc = 0, bs, buffer, idx = 0, output = "";
        // get next character
        (buffer = str.charAt(idx++));
        // character found in table? initialize bit storage and add its ascii value;
        ~buffer &&
        ((bs = bc % 4 ? bs * 64 + buffer : buffer),
            // and if not first of each 4 characters,
            // convert the first 8 bits to one ascii character
            bc++ % 4) ?
        (output += String.fromCharCode(255 & (bs >> ((-2 * bc) & 6)))) :
        0
    ) {
        // try to find character in table (0-63, not found => -1)
        buffer = chars.indexOf(buffer);
    }
    return output;
}

export default (typeof window !== "undefined" &&
    window.atob &&
    window.atob.bind(window)) ||
polyfill;