Your goal in this kata is to implement a difference function, which subtracts one list from another and returns the result.
It should remove all values from list a, which are present in list b.
array_diff([1,2],[1]) == [2]
If a value is present in b, all of its occurrences must be removed from the other:
array_diff([1,2,2,2,3],[2]) == [1,3]
my answer
const array_diff = (a, b) => a.filter(x => b.indexOf(x) === -1 );
best practice
function array_diff(a, b) {
return a.filter(e => !b.includes(e));
}