javascript数组去重

function unique(arr) {
  var result = [], hash = {};
      for (var i = 0, elem; (elem = arr[i]) != null; i++) {//循环arr数组
          if (!hash[elem]) {//hash数组作用：判断当前元素是否存在
              result.push(elem);//不存在：将当前元素存入到result数组中
              hash[elem] = true;//设置当前元素存在
              }
          }
          console.log(JSON.stringify(hash,null,2));//{"f": true,"a": true,"b": true,"c": true,"d": true,"e": true}
          return result;//返回去重后元素
        }
 var arr = ["f","a","b","c","a","a","b","d","e","e","f"];
 var result = unique(arr);
 console.log(result);//["f", "a", "b", "c", "d", "e"]