JavaScript中GBK和UTF-8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;
    }
}