Encode String with Base64 in Javascript

sample.html

<!-- Add some tags here, head, title etc and your references -->

<p>
  <label>Codificada:</label>
  <span id='1'></span>
</p>
<p>
  <label>Limpa:</label>
  <span id='2'></span>
</p>

<!-- Close body, html... -->

script.js

// Create Base64 Object
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
    }
}

// Define the string
var string = 'Minha string';

// Encode the String
var encodedString = Base64.encode(string);
$('span#1').text(encodedString);

// Decode the String
var decodedString = Base64.decode(encodedString);
$('span#2').text(decodedString);