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Data · easy

18. Map, Set and WeakMap

Keyed collections and garbage collection semantics.

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`Map` accepts arbitrary keys and maintains insertion order. `Set` enforces uniqueness. `WeakMap` only accepts objects as keys and does not prevent garbage collection.

js
const cache = new WeakMap();
const seen = new Set(["0x1", "0x2"]);

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  1. 1. What can be used as keys in a JavaScript Map?

  2. 2. Why use WeakMap for object-keyed metadata?

  3. 3. What does a Set enforce?

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