Missing key prop in React lists: warning and rendering bugs

When rendering arrays, I see this console warning: pgsql Copy code Warning: Each child in a list should have a unique "key" prop. Without keys, my items sometimes reorder or behave unpredictably, especially when the array changes. How do I resolve this?

React uses the key prop to track elements across renders. Missing or unstable keys (e.g. using index) can lead to mismatched state or unnecessary re-renders ([turn0reddit21]turn0search11). Fix: js Copy code list.map(item => ( <ItemComponent key={item.id} item={item} /> )) Use a stable and unique identifier, ideally not the array index. If using fragments: js Copy code <React.Fragment key={item.id}> {/* ... */} </React.Fragment> Correct keys eliminate rendering inconsistencies and suppress warnings.

📚 Category Web Development → Frontend → React → Hooks & Lifecycle / Performance & Rendering

🏷️ Suggested Tags pgsql Copy code react, react-hooks, useEffect, state update warning, cleanup, memory leaks, li