javascript代码：

    /**         *         *  Base64 encode / decode         *         *  @author haitao.tu         *  @date   2010-04-26         *  @email  tuhaitao@foxmail.com         *         */                     function Base64() {                         // private property              _keyStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";                         // public method for encoding              this.encode = function (input) {                  var output = "";                  var chr1, chr2, chr3, enc1, enc2, enc3, enc4;                  var i = 0;                  input = _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 +                      _keyStr.charAt(enc1) + _keyStr.charAt(enc2) +                      _keyStr.charAt(enc3) + _keyStr.charAt(enc4);                  }                  return output;              }                         // public method for decoding              this.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 = _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);                      }                  }                  output = _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;              }          }    

    <html>              <head>                  <script src="lib/base64.js" type="text/javascript"></script>                  <script type="text/javascript">                      var b = new Base64();                      var str = b.encode("admin:admin");                      alert("base64 encode:" + str);                      str = b.decode(str);                      alert("base64 decode:" + str);                  </script>              </head>              <body>              </body>          </html>