function diffArray(arr1, arr2) {

return arr1.filter(function (v) {

return arr2.indexOf(v) === -1;

}).concat(arr2.filter(function (v) {

return arr1.indexOf(v) === -1;

}));

}

/*

function diffArray (arr1, arr2) { return arr1.filter(n => !arr2.includes(n)).concat(arr2.filter(n => !arr1.includes(n))); }

*/

diffArray([1, 2, 3, 5], [1, 2, 3, 4, 5]); // should return an array.

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

["diorite", "andesite", "grass", "dirt", "dead shrub"]);

// should return ["pink wool"].

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

["diorite", "andesite", "grass", "dirt", "dead shrub"]);

// should return ["diorite", "pink wool"].

diffArray(["andesite", "grass", "dirt", "dead shrub"],

["andesite", "grass", "dirt", "dead shrub"]); // should return [].

diffArray([1, 2, 3, 5], [1, 2, 3, 4, 5]); // should return [4].

diffArray([1, "calf", 3, "piglet"], [1, "calf", 3, 4]);

// should return ["piglet", 4].

diffArray([], ["snuffleupagus", "cookie monster", "elmo"]);

// should return ["snuffleupagus", "cookie monster", "elmo"].

diffArray([1, "calf", 3, "piglet"], [7, "filly"]);

// should return [1, "calf", 3, "piglet", 7, "filly"].

/* Another option is as follows.

However, I really want to learn Array.Filter() and Array.indexOf();

function diffArray(arr1, arr2) {

var newArr = [];

// Same, same; but different.

for (var i = 0; i < arr1.length; i++){

if (arr2.indexOf(arr1[i]) < 0)

newArr.push(arr1[i]);

}

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

if (arr1.indexOf(arr2[j]) < 0)

newArr.push(arr2[j]);

}

return newArr;

}

*/