//找出字符串中第一个不重复的字符

 // firstUniqueChar("vdctdvc"); --> t

 function firstUniqueChar(str){

   var str = str || "",

       i = 0,

       k = "",

       _char = "",

       charMap = {},

       result = {name: "",index: str.length};

   for(i=0;i<str.length;i++){

     _char = str.charAt(i);

     if(charMap[_char] != undefined){

       charMap[_char] = -1;

     }else{

       charMap[_char] = i;

     }

   }

   for(k in charMap){

     if(charMap[k]<0){

       continue;

     }

     if(result.index>charMap[k]){

       result.index = charMap[k];

       result.name = k;

     }

   }

   return result.name;

 }