text: function diffArray(arr1, arr2) {
    var newArr = [];
  
    var test1 = "";
    var test2 = "";
  
    var resArr = [];
  
    newArr = arr1.concat(arr2);
    // Same, same; but different.
  
    var newSet = new Set(newArr);
  
    newSet.forEach( function(element, index) {
    	// statements
  
    	var test1 = newArr.indexOf(element);
    	var test2 = newArr.lastIndexOf(element);
    	if (test1 === test2){
    		resArr.push(element);
    	}
    });
    return resArr;
  
  }
  
  var res = diffArray([1, "calf", 3, "piglet"], [1, "calf", 3, 4]);
  console.log(res);