Missing Key Prop error

The Missing Key Prop error is a very common error that happens when we try to render a list without providing the key prop to the repeating children.

const Posts = () => {
  return (
    <ul>
      {posts.map((post) => (
        <Post post={post} />
        // ^ will throw the "Missing Key Prop"
      ))}
    </ul>
  );
};

In order to fix it, we need to provide the key prop that would be unique for every repeating child:

const Posts = () => {
  return (
    <ul>
      {posts.map((post) => (
        <Post key={post.id} post={post} />
        //     ^ the key prop is unique for all posts in this list
      ))}
    </ul>
  );
};

Reproduction

The example above will reproduce this error. Open your console to see the output.