var keyStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" + //all caps
"abcdefghijklmnopqrstuvwxyz" + //all lowercase
"0123456789+/="; // all numbers plus +/=

//Heres the encode function
function encode64(inp)
{
var out = ""; //This is the output
var chr1, chr2, chr3 = ""; //These are the 3 bytes to be encoded
var enc1, enc2, enc3, enc4 = ""; //These are the 4 encoded bytes
var i = 0; //Position counter

do { //Set up the loop here
chr1 = inp.charCodeAt(i++); //Grab the first byte
chr2 = inp.charCodeAt(i++); //Grab the second byte
chr3 = inp.charCodeAt(i++); //Grab the third byte

//Here is the actual base64 encode part.
//There really is only one way to do it.
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;
}

//Lets spit out the 4 encoded bytes
out = out + keyStr.charAt(enc1) + keyStr.charAt(enc2) + keyStr.charAt(enc3) +
keyStr.charAt(enc4);

// OK, now clean out the variables used.
chr1 = chr2 = chr3 = "";
enc1 = enc2 = enc3 = enc4 = "";

} while (i < inp.length); //And finish off the loop

//Now return the encoded values.
return out;
}

//Heres the decode function
function decode64(inp)
{
var out = ""; //This is the output
var chr1, chr2, chr3 = ""; //These are the 3 decoded bytes
var enc1, enc2, enc3, enc4 = ""; //These are the 4 bytes to be decoded
var i = 0; //Position counter

// remove all characters that are not A-Z, a-z, 0-9, +, /, or =
var base64test = /[^A-Za-z0-9\+\/\=]/g;

if (base64test.exec(inp)) { //Do some error checking
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.");
}
inp = inp.replace(/[^A-Za-z0-9\+\/\=]/g, "");

do { //Here’s the decode loop.

//Grab 4 bytes of encoded content.
enc1 = keyStr.indexOf(inp.charAt(i++));
enc2 = keyStr.indexOf(inp.charAt(i++));
enc3 = keyStr.indexOf(inp.charAt(i++));
enc4 = keyStr.indexOf(inp.charAt(i++));

//Heres the decode part. There’s really only one way to do it.
chr1 = (enc1 << 2) | (enc2 >> 4);
chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);
chr3 = ((enc3 & 3) << 6) | enc4;

//Start to output decoded content
out = out + String.fromCharCode(chr1);

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

//now clean out the variables used
chr1 = chr2 = chr3 = "";
enc1 = enc2 = enc3 = enc4 = "";

} while (i < inp.length); //finish off the loop

//Now return the decoded values.
return out;
}