Gives values present in any array.
Alternatives: compare, compare-update, map, map-update.
This is part of package extra-array.
array.unionOn$(x, y, [fn], [ths]);
// x: an array (updated)
// y: another array
// fn: map function (v, i, x)
// ths: this argument
// --> x
const array = require('extra-array');
var x = [1, 2, 3, 4];
array.unionOn$(x, [2, 3, 5]);
// [1, 2, 3, 4, 5]
x;
// [1, 2, 3, 4, 5]
var x = [1, 2, 3, 4];
array.unionOn$(x, [-2, -3, -5], v => Math.abs(v));
// [1, 2, 3, 4, -5]