[Deff]

Для включая старые ИЕ

var arr1=new Array('dsda','fjjd','fhhd','dsda','fhhd','dsda');
var arr2=[];
for(var i in arr1){
   var key=true;
   for(var j in arr2){
      if(arr2[j]==arr1[i]){key=false;break}
   }
   if(key)arr2.push(arr1[i]);
}
alert(arr2)