JS中utf8和GBK的字符编码转换

资料链接：http://igogogo9.iteye.com/blog/105669

1、PHP中的 json_encode 函数只限编码UTF-8的数据，当转换GBK或者GB2312等编码的数据时，会将汉字转为NULL。

2、JavaScript 中json 的使用：

① 将对象转为json字符串： JSON.stringify(obj) ② 将json转为对象： dataObj = eval('{"name":"Jack"}'); ③ 将PHP生成的json转为对象： dataObj = eval('(<?=json_encode(array('name'=>'Jack'))?>)');

3、JavaScript 中，GBK和UTF-8的转换：

function GB2312UTF8(){
this.Dig2Dec=function(s){
      var retV = 0;
      if(s.length == 4){
  for(var i = 0; i < 4; i ++){
      retV += eval(s.charAt(i)) * Math.pow(2, 3 - i);
  }
  return retV;
      }
      return -1;
} 
this.Hex2Utf8=function(s){
     var retS = "";
     var tempS = "";
     var ss = "";
     if(s.length == 16){
 tempS = "1110" + s.substring(0, 4);
 tempS += "10" + s.substring(4, 10); 
 tempS += "10" + s.substring(10,16); 
 var sss = "0123456789ABCDEF";
 for(var i = 0; i < 3; i ++){
    retS += "%";
    ss = tempS.substring(i * 8, (eval(i)+1)*8);
    retS += sss.charAt(this.Dig2Dec(ss.substring(0,4)));
    retS += sss.charAt(this.Dig2Dec(ss.substring(4,8)));
 }
 return retS;
     }
     return "";
} 
this.Dec2Dig=function(n1){
      var s = "";
      var n2 = 0;
      for(var i = 0; i < 4; i++){
 n2 = Math.pow(2,3 - i);
 if(n1 >= n2){
    s += '1';
    n1 = n1 - n2;
  }
 else
  s += '0';
      }
      return s;      
}

this.Str2Hex=function(s){
      var c = "";
      var n;
      var ss = "0123456789ABCDEF";
      var digS = "";
      for(var i = 0; i < s.length; i ++){
 c = s.charAt(i);
 n = ss.indexOf(c);
 digS += this.Dec2Dig(eval(n));
      }
      return digS;
}
this.Gb2312ToUtf8=function(s1){
    var s = escape(s1);
    var sa = s.split("%");
    var retV ="";
    if(sa[0] != ""){
      retV = sa[0];
    }
    for(var i = 1; i < sa.length; i ++){
      if(sa[i].substring(0,1) == "u"){
retV += this.Hex2Utf8(this.Str2Hex(sa[i].substring(1,5)));
   if(sa[i].length){
    retV += sa[i].substring(5);
   }
      }
      else{
     retV += unescape("%" + sa[i]);
   if(sa[i].length){
    retV += sa[i].substring(5);
   }
   }
    }
    return retV;
}
this.Utf8ToGb2312=function(str1){
var substr = "";
var a = "";
var b = "";
var c = "";
var i = -1;
i = str1.indexOf("%");
if(i==-1){
  return str1;
}
while(i!= -1){
    if(i<3){
substr = substr + str1.substr(0,i-1);
str1 = str1.substr(i+1,str1.length-i);
a = str1.substr(0,2);
str1 = str1.substr(2,str1.length - 2);
if(parseInt("0x" + a) & 0x80 == 0){
  substr = substr + String.fromCharCode(parseInt("0x" + a));
}
else if(parseInt("0x" + a) & 0xE0 == 0xC0){ //two byte
b = str1.substr(1,2);
str1 = str1.substr(3,str1.length - 3);
var widechar = (parseInt("0x" + a) & 0x1F) << 6;
widechar = widechar | (parseInt("0x" + b) & 0x3F);
substr = substr + String.fromCharCode(widechar);
}
else{
b = str1.substr(1,2);
str1 = str1.substr(3,str1.length - 3);
c = str1.substr(1,2);
str1 = str1.substr(3,str1.length - 3);
var widechar = (parseInt("0x" + a) & 0x0F) << 12;
widechar = widechar | ((parseInt("0x" + b) & 0x3F) << 6);
widechar = widechar | (parseInt("0x" + c) & 0x3F);
substr = substr + String.fromCharCode(widechar);
}
     }
     else {
      substr = substr + str1.substring(0,i);
      str1= str1.substring(i);
     }
      i = str1.indexOf("%");
}

return substr+str1;
}
}