1import React, { useState, useEffect } from 'react';
2
3const IntervalExample = () => {
4  const [seconds, setSeconds] = useState(0);
5
6  useEffect(() => {
7    const interval = setInterval(() => {
8      setSeconds(seconds => seconds + 1);
9    }, 1000);
10    return () => clearInterval(interval);
11  }, []);
12
13  return (
14    <div className="App">
15      <header className="App-header">
16        {seconds} seconds have elapsed since mounting.
17      </header>
18    </div>
19  );
20};
21
22export default IntervalExample;
23
24
25//__________________________________________//
26function Counter() {
27  let [count, setCount] = useState(0);
28  let [delay, setDelay] = useState(1000);
29
30  useInterval(() => {
31    // Your custom logic here
32    setCount(count + 1);
33  }, delay);
34
35  function handleDelayChange(e) {
36    setDelay(Number(e.target.value));
37  }
38
39  return (
40    <>
41      <h1>{count}</h1>
42      <input value={delay} onChange={handleDelayChange} />
43    </>
44  );
45}

1useEffect(() => {
2  const interval = setInterval(() => {
3    console.log('This will run every second!');
4  }, 1000);
5  return () => clearInterval(interval);
6}, []);

1function func(){
2  console.log("Ran")
3}
4setInterval(func,1000)//Runs the "func" function every second

1componentDidMount() {
2  this.interval = setInterval(() => this.setState({ time: Date.now() }), 1000);
3}
4componentWillUnmount() {
5  clearInterval(this.interval);
6}

1let myCounter = 0;
2let timeout = null;
3export default CounterApp = props => {
4
5  const [counter, setCounter] = useState(0);
6
7  // Also don't forget this
8  useEffect(()=> {
9    return ()=> clearInterval(timeout);
10  }, []);      
11
12  myCounter = counter;
13  const startInterval = () => {
14    timeout = setInterval(() => {
15      setCounter(counter => counter + 1);
16      console.log("counter: ", myCounter); // counter always return 0 but myCounter the updated value
17      if(myCounter === 10) clearInterval(timeout);
18
19    }, 1000);
20  };
21
22}
23

1timer: function() {
2   var newCount = this.state.currentCount - 1;
3   if(newCount >= 0) { 
4       this.setState({ currentCount: newCount });
5   } else {
6       clearInterval(this.state.intervalId);
7   }
8},
9