React gives us `useState` and `useRef` to store values across renders. But they behave differently. --- ## 1. useState - Stores **data that affects rendering**. - When state changes → component **re-renders**. - Best for values you want to **show in the UI**. ```tsx function Counter() { const [count, setCount] = useState(0) // 🔄 triggers re-render return ( ) } ``` Every click updates `count` → React re-renders → UI shows new value. --- ## 2. useRef - Stores a **mutable value** that survives re-renders. - Updating `.current` **does NOT trigger re-render**. - Best for storing **DOM nodes** or values that don’t affect UI. ```tsx function Timer() { const intervalRef = useRef(null) // 🗃️ stable across renders function start() { intervalRef.current = window.setInterval(() => { console.log("tick") }, 1000) } function stop() { if (intervalRef.current) clearInterval(intervalRef.current) } return ( <> ) } ``` Here, `intervalRef` keeps the timer ID but doesn’t cause re-renders. --- ## 3. When to Use Which? ✅ **Use `useState` when…** - The value **affects rendering**. - UI should update when value changes. - Examples: counters, form fields, theme toggles, fetched data. ✅ **Use `useRef` when…** - The value should **persist across renders** but doesn’t affect UI. - You want to avoid unnecessary re-renders. - Examples: - Accessing DOM elements (`ref={myRef}`) - Storing timer IDs, WebSocket connections - Holding previous values for comparison --- ## 4. Example: Using Both Together ```tsx function InputFocus() { const [text, setText] = useState("") // shows in UI const inputRef = useRef(null) // reference to DOM return ( <> setText(e.target.value)} /> ) } ``` - `useState` stores the text (triggers render). - `useRef` stores a DOM reference (no render needed). --- ## 5. Quick Mental Model 🧠 - **useState = for UI** → change → re-render. - **useRef = for storage** → change → no re-render. --- ## 6. Cheatsheet Table | Feature | `useState` ✅ | `useRef` ✅ | |---------------------|---------------|-------------| | **Triggers re-render on change** | ✔️ Yes | ❌ No | | **Best for** | UI values (text, count, toggles) | DOM refs, timers, storage | | **Persists across renders** | ✔️ Yes | ✔️ Yes | | **Mutable without causing render** | ❌ No | ✔️ Yes | | **Common uses** | Form inputs, counters, fetched data | Focus input, store IDs, previous values, WebSocket refs | --- ⚡ That’s it! Now you know when to reach for `useState` and when to grab `useRef` — and have a cheatsheet for quick reference.

Posts tagged “usestate”

React useRef vs useState — When to Use WhichNew