javascript 进行Base64编码

<html>

<body>

// 注意str应该是utf8
   function encode64(str) {
     var out, i, len;
      var c1, c2, c3;
      len = str.length;
      i = 0;
      out = "";
      while(i < len) {
          c1 = str.charCodeAt(i++) & 0xff;
          if(i == len) {
              out += base64EncodeChars.charAt(c1 >> 2);
              out += base64EncodeChars.charAt((c1 & 0x3) << 4);
              out += "==";
              break;
          }
          c2 = str.charCodeAt(i++);
          if(i == len) {
              out += base64EncodeChars.charAt(c1 >> 2);
              out += base64EncodeChars.charAt(((c1 & 0x3)<< 4) | ((c2 & 0xF0) >> 4));
              out += base64EncodeChars.charAt((c2 & 0xF) << 2);
              out += "=";
              break;
          }
          c3 = str.charCodeAt(i++);
          out += base64EncodeChars.charAt(c1 >> 2);
          out += base64EncodeChars.charAt(((c1 & 0x3)<< 4) | ((c2 & 0xF0) >> 4));
          out += base64EncodeChars.charAt(((c2 & 0xF) << 2) | ((c3 & 0xC0) >>6));
          out += base64EncodeChars.charAt(c3 & 0x3F);
      }
      return out;
   }

//--></script>
</script>
</body>
</html>