union$

Obtain values present in any array.

Alternatives: union, union$.
Similar: union, intersection, difference, symmetricDifference.

function union$(x, y, fc, fm)
// x:  an array (updated)
// y:  another array
// fc: compare function (a, b)
// fm: map function (v, i, x)

⏱️ Compare function => O(n²).

const array = require('extra-array');

var x = [1, 2, 3, 4];
var y = [2, 3, 5];
array.union$(x, y);
// → [ 1, 2, 3, 4, 5 ]

x;
// → [ 1, 2, 3, 4, 5 ]

var x = [1, 2, 3, 4];
var y = [-2, -3, -5];
array.union$(x, y, (a, b) => Math.abs(a) - Math.abs(b));
// → [ 1, 2, 3, 4, -5 ]

var x = [1, 2, 3, 4];
array.union$(x, y, null, v => Math.abs(v));
// → [ 1, 2, 3, 4, -5 ]

References

• Data.Set.union: Haskell
• Set.union: Python
• _.union: lodash
• _.unionBy: lodash
• _.unionWith: lodash
• Array.union: sugarjs