Example how to create key in list

react.key.jsx

import { v4 as uuidv4 } from "uuid";
import { useEffect, useState } from "react";

// Geting user from the "server"
function fetchUsers() {
  return fetch("/users")
    .then((x) => x.json())
    .then((users) => {
      return users.map((u) => {
        // creating the key with uuid package
        u.userKey = uuidv4();
        return u;
      });
    });
}

function AppList() {
  const [users, setUsers] = useState([]);

  useEffect(() => {
    fetchUsers().then(setUsers);
  }, []);

  return (
    <ul>
      {users.map(({ userKey, name }) => (
        <li key={userKey}>{name}</li>
      ))}
    </ul>
  );
}