1import React, { useState } from 'react';
2
3function Example() {
4  // Declaración de una variable de estado que llamaremos "count"  const [count, setCount] = useState(0);
5  return (
6    <div>
7      <p>You clicked {count} times</p>
8      <button onClick={() => setCount(count + 1)}>
9        Click me
10      </button>
11    </div>
12  );
13}

1const { useState, useEffect, useRef } = React;
2
3function useInterval(callback, delay) {
4  const savedCallback = useRef();
5
6  // Remember the latest callback.
7  useEffect(() => {
8    savedCallback.current = callback;
9  }, [callback]);
10
11  // Set up the interval.
12  useEffect(() => {
13    let id = setInterval(() => {
14      savedCallback.current();
15    }, delay);
16    return () => clearInterval(id);
17  }, [delay]);
18}
19
20function App() {
21  const [counter, setCounter] = useState(0);
22
23  useInterval(() => {
24    setCounter(counter + 1);
25  }, 1000);
26
27  return <h1>{counter}</h1>;
28};
29
30ReactDOM.render(
31  <App />,
32  document.getElementById('root')
33);