es6_set.js

var arr = [2,3,4,5,2,4];

//Without Set
var tempArr = arr.filter(function(item,index){
 return arr.indexOf(item) == index;
});

console.log(tempArr.length); //4


//With Set
var set = new Set();

arr.forEach(function(item){
  set.add(item);
});


console.log(set.size); //4