Code for Base64 Encoding and Decoding of String – Javascript

What is Base64?
Base64 is a generic term for a number of similar encoding schemes that encode binary data by treating it numerically and translating it into a base 64 representation. The Base64 term originates from a specific MIME content transfer encoding.

Base64 encoding schemes are commonly used when there is a need to encode binary data that needs be stored and transferred over media that are designed to deal with textual data. This is to ensure that the data remains intact without modification during transport. Base64 is used commonly in a number of applications including email via MIME, and storing complex data in XML and in while sending usernames and passwords over network for authentication.

Below javascript snippet lets you to encode and decode your strings using Base64.

var Base64 = {

        keyStr: 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=',

        encode: function (input) {
            var output = "";
            var chr1, chr2, chr3 = "";
            var enc1, enc2, enc3, enc4 = "";
            var i = 0;

            do {
                chr1 = input.charCodeAt(i++);
                chr2 = input.charCodeAt(i++);
                chr3 = input.charCodeAt(i++);

                enc1 = chr1 >> 2;
                enc2 = ((chr1 & 3) << 4) | (chr2 >> 4);
                enc3 = ((chr2 & 15) << 2) | (chr3 >> 6);
                enc4 = chr3 & 63;

                if (isNaN(chr2)) {
                    enc3 = enc4 = 64;
                } else if (isNaN(chr3)) {
                    enc4 = 64;
                }

                output = output +
                    this.keyStr.charAt(enc1) +
                    this.keyStr.charAt(enc2) +
                    this.keyStr.charAt(enc3) +
                    this.keyStr.charAt(enc4);
                chr1 = chr2 = chr3 = "";
                enc1 = enc2 = enc3 = enc4 = "";
            } while (i < input.length);

            return output;
        },

        decode: function (input) {
            var output = "";
            var chr1, chr2, chr3 = "";
            var enc1, enc2, enc3, enc4 = "";
            var i = 0;

            // remove all characters that are not A-Z, a-z, 0-9, +, /, or =
            var base64test = /[^A-Za-z0-9\+\/\=]/g;
            if (base64test.exec(input)) {
                window.alert("There were invalid base64 characters in the input text.\n" +
                    "Valid base64 characters are A-Z, a-z, 0-9, '+', '/',and '='\n" +
                    "Expect errors in decoding.");
            }
            input = input.replace(/[^A-Za-z0-9\+\/\=]/g, "");

            do {
                enc1 = this.keyStr.indexOf(input.charAt(i++));
                enc2 = this.keyStr.indexOf(input.charAt(i++));
                enc3 = this.keyStr.indexOf(input.charAt(i++));
                enc4 = this.keyStr.indexOf(input.charAt(i++));

                chr1 = (enc1 << 2) | (enc2 >> 4);
                chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);
                chr3 = ((enc3 & 3) << 6) | enc4;

                output = output + String.fromCharCode(chr1);

                if (enc3 != 64) {
                    output = output + String.fromCharCode(chr2);
                }
                if (enc4 != 64) {
                    output = output + String.fromCharCode(chr3);
                }

                chr1 = chr2 = chr3 = "";
                enc1 = enc2 = enc3 = enc4 = "";

            } while (i < input.length);

            return output;
        }
    };