React Warning: flattenChildren(…): Encountered two children with the same key

by

It is not a good idea to use the index as the key. A key is the only thing React uses to identify DOM elements. What happens if you push an item to the list or remove something in the middle? If the key is same as before React assumes that the DOM element represents the same component as before. But that is no longer true. From: https://medium.com/@robinpokorny/index-as-a-key-is-an-anti-pattern-e0349aece318

It is much better to use a unique string from each item you are mapping over as the key. Something like <option key={value.id}> or if a key does not exist, create a unique identifier by doing something like <option key={value.name + value.description}>.

More Related Contents:

  1. Uncaught Error: Invariant Violation: Element type is invalid: expected a string (for built-in components) or a class/function but got: object
  2. Link tag inside BrowserRouter changes only the URL, but doesn’t render the component
  3. OnClick Event binding in React.js
  4. What is event pooling in react?
  5. React doesn’t reload component data on route param change or query change
  6. Can I add a key prop to a React fragment?
  7. How to add multiple classes to a ReactJS Component?
  8. Typescript: React event types
  9. componentDidMount called BEFORE ref callback
  10. firebase.auth is not a function
  11. Use componentWillMount or componentDidMount lifecycle functions for async request in React
  12. Best way to polyfill ES6 features in React app that uses create-react-app
  13. Determine which dependency array variable caused useEffect hook to fire
  14. What does “export default” do in JSX?
  15. Axios – DELETE Request With Request Body and Headers?
  16. Updating state to the same state directly in the component body
  17. reactjs and masonry layout – undefined
  18. Jest – SyntaxError: Cannot use import statement outside a module
  19. useMemo vs. useEffect + useState
  20. JSX not allowed in files with extension ‘ .js’ with eslint-config-airbnb
  21. Nothing was returned from render. This usually means a return statement is missing. Or, to render nothing, return null [closed]
  22. React-Redux: Should all component states be kept in Redux Store
  23. React.js best practice regarding listening to window events from components
  24. how to render child components in react.js recursively
  25. React’s setState method with prevState argument
  26. TypeError: Cannot read properties of undefined (reading ‘call’) on Next.js
  27. Updating state to the same value directly in the component body during render causes infinite loop
  28. Preserve Type when using Object.entries
  29. React Hooks render twice
  30. How to preload images in React.js?

Leave a Comment