union$

Obtain entries present in any map.

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

function union$(x, y, fc)
// x:  a map (updated)
// y:  another map
// fc: combine function (a, b)

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

var x = new Map([['a', 1],  ['b', 2],  ['c', 3]]);
var y = new Map([['b', 20], ['c', 30], ['d', 40]]);
map.union$(x, y);
// → Map(4) { 'a' => 1, 'b' => 2, 'c' => 3, 'd' => 40 }

x;
// → Map(4) { 'a' => 1, 'b' => 2, 'c' => 3, 'd' => 40 }

var x = new Map([['a', 1],  ['b', 2],  ['c', 3]]);
var y = new Map([['b', 20], ['c', 30], ['d', 40]]);
map.union$(x, y, (a, b) => b);
// → Map(4) { 'a' => 1, 'b' => 20, 'c' => 30, 'd' => 40 }

References

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