Base64-encoded data takes about 33% more space than the original data, but it is useful when you want to transfer compact and encrypted data from an aplication to another (for example from cliend side /browser to a script on server and vice versa).
In this page it is presented a JavaScript object that can be used to
encode / decode data with MIME base64 . This object is fully compatible with UTF-8 encoding.
-
Source code of Base64 object, from
http://www.webtoolkit.info/javascript-base64.html.
/**
* Base64 encode / decode
* http://www.webtoolkit.info/
**/
var Base64 = {
// private property
_keyStr : "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=",
// public method for encoding
encode : function (input) {
var output = "";
var chr1, chr2, chr3, enc1, enc2, enc3, enc4;
var i = 0;
input = Base64._utf8_encode(input);
while (i < input.length) {
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);
}
return output;
},
// public method for decoding
decode : function (input) {
var output = "";
var chr1, chr2, chr3;
var enc1, enc2, enc3, enc4;
var i = 0;
input = input.replace(/[^A-Za-z0-9\+\/\=]/g, "");
while (i < input.length) {
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);
}
}
output = Base64._utf8_decode(output);
return output;
},
// private method for UTF-8 encoding
_utf8_encode : function (string) {
string = string.replace(/\r\n/g,"\n");
var utftext = "";
for (var n = 0; n < string.length; n++) {
var c = string.charCodeAt(n);
if (c < 128) {
utftext += String.fromCharCode(c);
}
else if((c > 127) && (c < 2048)) {
utftext += String.fromCharCode((c >> 6) | 192);
utftext += String.fromCharCode((c & 63) | 128);
}
else {
utftext += String.fromCharCode((c >> 12) | 224);
utftext += String.fromCharCode(((c >> 6) & 63) | 128);
utftext += String.fromCharCode((c & 63) | 128);
}
}
return utftext;
},
// private method for UTF-8 decoding
_utf8_decode : function (utftext) {
var string = "";
var i = 0;
var c = c1 = c2 = 0;
while ( i < utftext.length ) {
c = utftext.charCodeAt(i);
if (c < 128) {
string += String.fromCharCode(c);
i++;
}
else if((c > 191) && (c < 224)) {
c2 = utftext.charCodeAt(i+1);
string += String.fromCharCode(((c & 31) << 6) | (c2 & 63));
i += 2;
}
else {
c2 = utftext.charCodeAt(i+1);
c3 = utftext.charCodeAt(i+2);
string += String.fromCharCode(((c & 15) << 12) | ((c2 & 63) << 6) | (c3 & 63));
i += 3;
}
}
return string;
}
}
-
Usage:
1. Copy the Base64 object into your JavaScript script.
2. To encode a string, calls the encode() method:
Base64.encode('string'); .
3. To decode a base64-encoded string, calls the decode() method:
Base64.decode('base64-string'); .
- Example. The text added into a textarea will be encoded with base64, and added into an input form field. The base64-encoded string added in that input field can be decoded and displayed into an Alert window.
<form action="#" method="post">
Enter a text:<br/>
<textarea name="txtstr" id="txtstr" cols="26" rows="5"></textarea> <button id="btnencode64">Encode</button><br/><br/>
Base64 encoded data:<br/>
<input type="text" name="str64" id="str64" size="34" /> <button id="btndecode64">Decode</button>
</form>
<script type="text/javascript">
// Here add the code of Base64 object
// register onclick events for encode button
document.getElementById('btnencode64').onclick = function() {
var txt_string = document.getElementById('txtstr').value; // gets data from textarea
// encode data and adds it in #str64 element
document.getElementById('str64').value = Base64.encode(txt_string);
return false;
}
// register onclick events for decode button
document.getElementById('btndecode64').onclick = function() {
// decode data from input text field and display it into an alert window
var str64 = Base64.decode(document.getElementById('str64').value);
alert(str64);
return false;
}
</script>
Demo: