JavaScript base64编(解)码函数

转自：http://blog.sina.com.cn/s/blog_3f195d2501007xki.html

<!--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);}//-->