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javascript UTF16转Utf8

 function utf16to8(str) {
     var out, i, len, c;

     out = "";
     len = str.length;
     for(i = 0; i < len; i++) {   c = str.charCodeAt(i);   if ((c >= 0x0001) && (c <= 0x007F)) {       out += str.charAt(i);   } else if (c > 0x07FF) {
      out += String.fromCharCode(0xE0 | ((c >> 12) & 0x0F));
      out += String.fromCharCode(0x80 | ((c >>  6) & 0x3F));
      out += String.fromCharCode(0x80 | ((c >>  0) & 0x3F));
  } else {
      out += String.fromCharCode(0xC0 | ((c >>  6) & 0x1F));
      out += String.fromCharCode(0x80 | ((c >>  0) & 0x3F));
  }
     }
     return out;
 }

javascript UTF8转Utf16

 function utf8to16(str) {
     var out, i, len, c;
     var char2, char3;

     out = "";
     len = str.length;
     i = 0;
     while(i < len) {   c = str.charCodeAt(i++);   switch(c >> 4)
  {
    case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7:
      // 0xxxxxxx
      out += str.charAt(i-1);
      break;
    case 12: case 13:
      // 110x xxxx   10xx xxxx
      char2 = str.charCodeAt(i++);
      out += String.fromCharCode(((c & 0x1F) << 6) | (char2 & 0x3F));
      break;
    case 14:
      // 1110 xxxx  10xx xxxx  10xx xxxx
      char2 = str.charCodeAt(i++);
      char3 = str.charCodeAt(i++);
      out += String.fromCharCode(((c & 0x0F) << 12) |
         ((char2 & 0x3F) << 6) |
         ((char3 & 0x3F) << 0));
      break;
  }
     }

     return out;
 }

from http://www.blogjava.net/Carter0618/archive/2009/06/16/282539.html