When would you use Map/Set over plain objects/arrays?
Quick answer
Map for keyed collections with any key type and ordered, sized iteration; Set for unique values and fast membership.
In detail
A Map allows any key (objects included), preserves insertion order, has `.size`, and is optimised for frequent adds/deletes — better than an object for a true dictionary. A Set stores unique values with O(1) `has`, ideal for de-duplication and membership checks.
const m = new Map();
m.set(objKey, 1); m.get(objKey); m.size;
const s = new Set([1, 2, 2]); s.has(2); // true, size 2Why interviewers ask this: Tests data-structure judgement beyond objects/arrays.
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