JS Array Methods

Essential array methods: map (transform each item), filter (keep matching items), reduce (combine into single value), find (first match), some/every (boolean tests), forEach (side effects), sort (order items), flat/flatMap (flatten nested arrays), includes (check membership), slice (extract portion without mutation), splice (add/remove in place). Chain them: users.filter(u => u.active).map(u => u.name).sort(). Immutable methods (map, filter, slice) are preferred over mutating methods (sort, splice).