b64.js

var Base64 = ( function(  ) {

          var _PADCHAR = "=",
            _ALPHA = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";


          function _getbyte( s, i ) {
            var x = s.charCodeAt( i );

            if ( x > 255 ) {
              throw "INVALID_CHARACTER_ERR: DOM Exception 5";
            }

            return x;
          }


          function _encode( s ) {
            if ( arguments.length !== 1 ) {
              throw "SyntaxError: exactly one argument required";
            }

            s = String( s );

            var i,
              b10,
              x = [],
              imax = s.length - s.length % 3;

            if ( s.length === 0 ) {
              return s;
            }

            for ( i = 0; i < imax; i += 3 ) {
              b10 = ( _getbyte( s, i ) << 16 ) | ( _getbyte( s, i + 1 ) << 8 ) | _getbyte( s, i + 2 );
              x.push( _ALPHA.charAt( b10 >> 18 ) );
              x.push( _ALPHA.charAt( ( b10 >> 12 ) & 0x3F ) );
              x.push( _ALPHA.charAt( ( b10 >> 6 ) & 0x3f ) );
              x.push( _ALPHA.charAt( b10 & 0x3f ) );
            }

            switch ( s.length - imax ) {
              case 1:
                b10 = _getbyte( s, i ) << 16;
                x.push( _ALPHA.charAt( b10 >> 18 ) + _ALPHA.charAt( ( b10 >> 12 ) & 0x3F ) + _PADCHAR + _PADCHAR );
                break;

              case 2:
                b10 = ( _getbyte( s, i ) << 16 ) | ( _getbyte( s, i + 1 ) << 8 );
                x.push( _ALPHA.charAt( b10 >> 18 ) + _ALPHA.charAt( ( b10 >> 12 ) & 0x3F ) + _ALPHA.charAt( ( b10 >> 6 ) & 0x3f ) + _PADCHAR );
                break;
            }

            return x.join( "" );
          }


          return {
            encode: _encode
          };

    })();