javascript base64編碼解碼

最後更新：2018-12-03 來源：互聯網

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<html>

<body>
<script language="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>

<form method="POST" action="--WEBBOT-SELF--">
<table border="1" width="100%" style="border-collapse: collapse">
    <tr>
        <td><textarea rows="20" name="S1" cols="57"></textarea></td>
        <td><input type="button" value="base64decode-->" name="B1" onclick="S2.value=decode64(S1.value);"><br>
        <input type="button" value="<--base64encode" name="B2" onclick="S1.value=encode64(S2.value)"></td>
        <td><textarea rows="20" name="S2" cols="56"></textarea></td>
    </tr>
    <tr>
        <td>　</td>
        <td>　</td>
        <td>　</td>
    </tr>
</table>

</form>
</body>

</html>

本文章原先以中文撰寫並發佈於 aliyun.com，亦設英文版本，僅作資訊用途。本網站不對文章的準確性，完整性或可靠性或其任何翻譯作出任何明示或暗示的陳述或保證。如對該文章有任何疑慮或投訴，請傳送電郵至 info-contact@alibabacloud.com 並提供相關疑慮或投訴的詳細說明。職員會於 5 個工作天內與您聯絡，一經驗證之後，即會刪除該侵權內容。

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