How to Clear Timeout and interval Timers with React Hooks?

How to Clear Timeout and interval Timers with React Hooks?

Timers created with clearTimeout or setInterval are used often timers in React apps. To clearTimeout that are created with setTimeout , we should call clearTimeout(timer) in the useEffect. How to Clear Timeout and Interval Timers with React Hooks?

Timers created with setTimeout or setInterval are used often in React apps.

setTimeout lets us run code after a delay.

And setInterval lets us run code periodically.

To free up resources and to stop the timers from running, we should call clearTimeout to stop any timers created with setTimeout from running.

Likewise, we should call clearInterval to stop any timers created with setInterval from running.

In this article, we’ll look at the right way to clear timers created with these functions in React components created with hooks.

Clear Timers Created with setTimeout

To clear timers that are created with setTimeout , we should call clearTimeout in the useEffect callback is the function that’s run when the component unmounts.

The function that we return in the useEffect callback is run when the component unmounts, so we should put it there,.

For instance, we can write:

import React, { useEffect, useState } from "react";

export default function App() {
  const [loading, setLoading] = useState(true);
  useEffect(() => {
    const timer = setTimeout(() => setLoading(false), 1000);
    return () => {
      clearTimeout(timer);
    };
  }, []);
  return <div>{loading ? "loading" : "hello"}</div>;
}

We have the loading state which is initially set to true .

Then we call useEffect with a callback.

In the callback, we call setTimeout with a callback that calls setLoading with false to set loading to false .

And the callback is run after 1000 milliseconds since the 2nd argument is 1000.

Also, we return a function that calls clearTimeout with timer to clear the timer.

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