javascript base 64 인 코딩 디 코딩

var keyStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";

function encode64(input)
{
	input = escape(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 +
		keyStr.charAt(enc1) +
		keyStr.charAt(enc2) +
		keyStr.charAt(enc3) +
		keyStr.charAt(enc4);
		chr1 = chr2 = chr3 = "";
		enc1 = enc2 = enc3 = enc4 = "";
	} while (i < input.length);

	return output;
}

function decode64(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))
	{
		alert("There were invalid base64 characters in the input text.
" +
		"Valid base64 characters are A-Z, a-z, 0-9, '+', '/', and '='
" +
		"Expect errors in decoding.");
	}
	input = input.replace(/[^A-Za-z0-9\+\/\=]/g, "");

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


document.writeln(encode64("   "));
alert(decode64("JXU0RjYwJXU1OTdEJXU1NTRB"));