how to call api on load using hooks in react

1function User() {
2  const [firstName, setFirstName] = React.useState(null);
3  const [lastName, setLastName] = React.useState(null);
4  
5  React.useEffect(() => {
6    fetch('https://randomuser.me/api/')
7      .then(results => results.json())
8      .then(data => {
9        const {name} = data.results[0];
10        setFirstName(name.first);
11        setLastName(name.last);
12      });
13  }, []); // <-- Have to pass in [] here!
14
15  return (
16    <div>
17      Name: {!firstName || !lastName ? 'Loading...' : `${firstName} ${lastName}`}
18    </div>
19  );
20}
21
22ReactDOM.render(<User />, document.querySelector('#app'));