1let difference = arr1.filter(x => !arr2.includes(x));

1function arrayDiff (a1, a2) {
2    var a = [], diff = [];
3    for (var i = 0; i < a1.length; i++) {
4        a[a1[i]] = true;
5    }
6    for (var i = 0; i < a2.length; i++) {
7        if (a[a2[i]]) {
8            delete a[a2[i]];
9        } else {
10            a[a2[i]] = true;
11        }
12    }
13    for (var k in a) {
14        diff.push(k);
15    }
16    return diff;
17}
18//usage:
19console.log(arrayDiff(['red', 'white','green'], [ 'red','white', 'blue']));//["green", "blue"]