function diffArray(arr1, arr2) {
  var newArr = [];
  var str2 = arr2.join(",");
  var str1 = arr1.join(",");
  alert(str2);
  for (var i = 0; i < arr1.length; i++) {


  	if (str2.indexOf(arr1[i]) === -1  ) {
  		newArr.push(arr1[i]);
  		}

  }

  for (var j = 0; j < arr2.length; j++) {


  	if (str1.indexOf(arr2[j]) === -1  ) {
  		newArr.push(arr2[j]);
  		}

  }




  return newArr;
}


diffArray(["diorite", "andesite", "grass", "dirt", "pink wool", "dead shrub"], ["diorite", "andesite", "grass", "dirt", "dead shrub"]);