unionKeys - nodef/extra-map GitHub Wiki

Obtain keys present in any map.

Similar: unionKeys, intersectionKeys. Similar: union, intersection, difference, symmetricDifference, isDisjoint.

function unionKeys(...xs)
// xs: maps
const map = require('extra-map');

var x = new Map(['a', 1],  ['b', 2],  ['c', 3], ['d', 4](/nodef/extra-map/wiki/'a',-1],--['b',-2],--['c',-3],-['d',-4));
var y = new Map(['b', 20], ['c', 30], ['e', 50](/nodef/extra-map/wiki/'b',-20],-['c',-30],-['e',-50));
map.unionKeys(x, y);
// → Set(5) { 'a', 'b', 'c', 'd', 'e' }

References