State Basics with useState

The useState Hook

const [count, setCount] = useState(0);
setCount(c => c + 1);

Updating Objects and Arrays

Never mutate - spread into new values so React detects the change.

setUser(p => ({ ...p, email: next }));
setItems(p => [...p, item]);

State vs Props

State is local and mutable via its setter; props come from the parent and are read-only.

Key Points

• State updates are async and may batch.
• Use functional updates when state depends on previous state.
• Lift shared state to the common parent.