code: function encode2UTF8(charCode){
      if(charCode <= 0x7f){
        return [charCode];
      }else if(charCode <= 0x7ff){
        return [0xc0|(charCode>>6), 0x80|(charCode & 0x3f)];
      }else{
        return [0xe0|(charCode>>12), 0x80|((charCode & 0xfc0)>>6), 0x80|(charCode & 0x3f)];
      }
    }
docs: Encode a unicode16 char code to utf8 bytes