JS中数组去重

var str = "1,2,4,5,2,4";
 
 var s = str.split(',');
 var dic = {};  
 for (var i = s.length; i--; ) {
  dic[s[i]]=s[i];
  }      
 var r = [];      
 for (var v in dic) {
  r.push(dic[v]);
 }    
 alert(r.join());