const numbers = [1, 2, 3, 4, 5]; 
const listItems = numbers.map((number) => 
 <li>{number}</li>
);
ReactDOM.render( 
 <ul>{listItems}</ul>,
 document.getElementById('root')
);

function NumberList(props) { 
 const numbers = props.numbers;
 const listItems = numbers.map((number) =>
 <li key={number.toString()}>
  {number}
 </li>
 );
 return (
 <ul>{listItems}</ul>
 );
}

const numbers = [1, 2, 3, 4, 5]; 
ReactDOM.render( 
 <NumberList numbers={numbers} />,
 document.getElementById('root')
);

const todoItems = todos.map((todo) => 
 <li key={todo.id}>
 {todo.text}
 </li>
);
const todoItems = todos.map((todo, index) => 
 // Only do this if items have no stable IDs
 <li key={index}>
 {todo.text}
 </li>
);

function NumberList(props) { 
 const numbers = props.numbers;
 const listItems = numbers.map((number) =>
 <ListItem key={number.toString()}
    value={number} />
 );
 return (
 <ul>
  {listItems}
 </ul>
 );
}

function NumberList(props) { 
 const numbers = props.numbers;
 return (
 <ul>
  {numbers.map((number) =>
  <ListItem key={number.toString()}
     value={number} />
  )}
 </ul>
 );
}