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Set & WeakSet

Easy

In plain terms

Set stores unique values (no duplicates). Methods: add, has, delete, size. WeakSet holds objects only; does not prevent garbage collection. Iterable with for...of.

What you need to know

  • •Unique values only
  • •add, has, delete
  • •WeakSet: objects only, weak refs

Try it yourself

Copy the code below and run it in your browser console or a code editor:

const set = new Set([1, 2, 2, 3]);
set;           // Set(3) {1, 2, 3}
set.add(4);
set.has(2);    // true
set.delete(2);
set.size;      // 3

for (const v of set) {
  console.log(v);
}

const ws = new WeakSet();
ws.add({});    // only objects
// No size, no iteration

Learn more

Dive deeper with these trusted resources:

MDNjavascript.infoTutorialsPointW3Schools