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别人的一段javascript base64加/解脚本.

工程师
2014-08-22 14:07:04     打赏

<html>
<head>
<title>base64 Encoding/Decoding</title>
</head>
<script type="text/javascript"><!--
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>
<body>
<form name="base64Form">
   Type in the message you want to encode in base64, or paste<br>
   base64 encoded text into the text field, select Encode or Decode, <br>
   and click the button!<br>


   <textarea name="theText" cols="40" rows="6"></textarea><br>


   <input type="button" name="encode" value="Encode to base64"
      onClick="document.base64Form.theText.value=encode64(document.base64Form.theText.value);">
   <input type="button" name="decode" value="Decode from base64" 
      onClick="document.base64Form.theText.value=decode64(document.base64Form.theText.value);">
</form>
</body>
</html


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