Javascript Base64加密解密代码

<script language="javascript" runat="server">  
var keyStr = "ABCDEFGHIJKLMNOP" +  
             "QRSTUVWXYZabcdef" +  
             "ghijklmnopqrstuv" +  
             "wxyz0123456789+/" +  
             "=";  
  
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.\n" +  
            "Valid base64 characters are A-Z, a-z, 0-9, ‘+‘, ‘/‘, and ‘=‘\n" +  
            "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);  
}  
</script>