JavaScript Set_basics Guide
Set stores unique values of any type. Useful for deduplication, membership testing, and mathematical set operations. The guide walks through Set Operations. `new Set([1,2,3])` — create. `.add(val)` — add. `.has(val)` — check. `.delete(val)` — remove. `.size` — count. `.clear()` — empty. `[...new Set(arr)]` — deduplicate array. Intersection: `[...a].filter(x => b.has(x))`. Difference: `[...a].filter(x => !b.has(x))`. Union: `new Set([...a, ...b])`. The guide is organized into 1 sections that build on each other, each pairing a prose explanation with runnable code. Related guides: Arrays, Strings, Numbers, Math, Date. This is one of 145 JavaScript guides on JS Reference — see the full list on the guides page. Practice what you learn in the JavaScript playground, and look up any unfamiliar term in the JavaScript glossary.