key element react code example

Example 1: map function in react

function NameList() {
	const names = ['Bruce', 'Clark', 'Diana']
    return (
    	<div>
      {names.map(name => <h2>{name}</h2>)}
      	</div>
    )
}

Example 2: react component key prop

function ListItem(props) {
  // Correct! There is no need to specify the key here:  return <li>{props.value}</li>;}

function NumberList(props) {
  const numbers = props.numbers;
  const listItems = numbers.map((number) =>
    // Correct! Key should be specified inside the array.    <ListItem key={number.toString()} value={number} />  );
  return (
    <ul>
      {listItems}
    </ul>
  );
}

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