js diff

function diff(arr1, arr2) {
  var newArr = [];
  
  var diff1 = arr1.filter(function(val){
      return -1 == arr2.indexOf(val);
  });
  var diff2 = arr2.filter(function(val){
      return -1 == arr1.indexOf(val);
  });
  
  newArr = diff1.concat(diff2);
  
  return newArr;
}

var diffArr = diff([1, 2, 3, 5], [1, 2, 3, 4, 5]);
console.log(diffArr)