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How to clear setTimeout when the page is changed in reactjs - nextjs

I created a slideshow in the Nextjs project, But I have a bug. When the user clicks on a link and the page has changed I get an Unhandled Runtime Error and I know it because of the setTimeout function it calls a function and tries to style an element that does not exist on the new page.
How can I clear the setTimeout function after the user click the links?
Error screenshot:
My component code:
import { useEffect, useState } from "react";
import SlideContent from "./slide-content";
import SlideDots from "./slide-dots";
import SlideItem from "./slide-item";
const Slide = (props) => {
const { slides } = props;
const [slideLength, setSlideLength] = useState(slides ? slides.length : 0);
const [slideCounter, setSlideCounter] = useState(1);
const handleSlideShow = () => {
if (slideCounter < slideLength) {
document.querySelector(
`.slide-content:nth-of-type(${slideCounter})`
).style.left = "100%";
const setSlide = slideCounter + 1;
setSlideCounter(setSlide);
setTimeout(() => {
document.querySelector(
`.slide-content:nth-of-type(${setSlide})`
).style.left = 0;
}, 250);
} else {
document.querySelector(
`.slide-content:nth-of-type(${slideCounter})`
).style.left = "100%";
setSlideCounter(1);
setTimeout(() => {
document.querySelector(`.slide-content:nth-of-type(1)`).style.left = 0;
}, 250);
}
};
useEffect(() => {
if (slideLength > 0) {
setTimeout(() => {
handleSlideShow();
}, 5000);
}
}, [slideCounter, setSlideCounter]);
return (
<>
<div className="slide-button-arrow slide-next">
<span className="carousel-control-prev-icon"></span>
</div>
<div className="slide">
{slides.map((slide) => (
<SlideContent key={`slide-${slide.id}`}>
<SlideItem img={slide.img} title={slide.title} />
</SlideContent>
))}
<SlideDots activeDot={slideCounter} totalDots={slides} />
</div>
<div className="slide-button-arrow slide-prev">
<span className="carousel-control-next-icon"></span>
</div>
</>
);
};
export default Slide;
I use my slideshow component inside the home page file.

useEffect(() => {
let timer;
if (slideLength > 0) {
timer=setTimeout(() => {
handleSlideShow();
}, 5000);
}
return () => {
clearTimeout(timer);
};
}, [slideCounter, setSlideCounter]);

you should remove your timeout function when the component unmounts.
(if you're using old syntax there is componentWillUnmount() function)
when you are using hooks you can return your useEffect so it will cause the unmount function.
in your case it will be something like this:
useEffect(() => {
//define a temp for your timeout to clear it later
let myTimeout;
if (slideLength > 0) {
//assign timeout function to the variable
myTimeout = setTimeout(() => {
handleSlideShow();
}, 5000);
}
// this triggers when the component unmounts or gets re-rendered.
// you can clear the timeout here.
return () => {
clearTimeout(myTimeout);
}
}, [slideCounter, setSlideCounter]);
you should always remove your timeouts because you don't want memory leaks and performance issues. it might not give you errors but clear them all.
there is an old post i guess you can read here

Stopwatch in react and useInterval

I am trying to create a stop watch using react and set interval but do not understand why count variable is always 0 is it being reset to default state. I thought since state takes some time to update hence count was always 0 but even if i increase the set interval timer it shows the same value.
Through i am trying to understand how react hooks work if someone can shed some light on functioning of hooks or redirect me to necessary links please do so
code is working in case i replace setCount(count+1) to setCount(prevCount=>prevCount+1) also you need to declare intervalId outside of app function
import "./styles.css";
import { useState } from "react";
export default function App() {
const [count, setCount] = useState(0);
let intervalId = -1;
const increment = () => {
console.log(count);
setCount(count + 1);
};
const handleStart = () => {
if (intervalId === -1)
intervalId = setInterval(() => {
// console.log("called");
increment();
}, 1000);
};
const handleStop = () => {
clearInterval(intervalId);
setCount(0);
};
const handlePause = () => {
clearInterval(intervalId);
};
const handleResume = () => {
handleStart();
};
return (
<div className="App">
<div className="counter">{count}</div>
<button onClick={handleStart} className="counter">
start
</button>
<button onClick={handleStop} className="counter">
stop
</button>
<button onClick={handlePause} className="counter">
pause
</button>
<button onClick={handleResume} className="counter">
resume
</button>
</div>
);
}

I'm by no means a React expert, but I watched this talk before and found it very enlightening, and I recommend you watch it too.
I also recommend you watch the first part, but the timestamp I linked is more relevant to your question.
Now in the official react docs here, they say:
If the new state is computed using the previous state, you can pass a function to setState. The function will receive the previous value, and return an updated value.
So, as you noticed with prevCount, it works when you do it that.
In this blog post, the writer explains that:
if you increment the count value as follows setCount(count + 1)
The the count will stuck at 0 + 1 = 1 because the variable count value when setInterval() is called is 0.
So we know that we need the previous state. If you follow the blog post, he does set up a working counter.
The way the code is right now will create an interval for each click since the intervalID gets set to -1 with each update. So, similar to the blogpost, we can have the interval ID as a state. Here's your stopwatch using that approach:
CodeSandbox
import "./styles.css";
import { useState } from "react";
export default function App() {
const [count, setCount] = useState(0);
const [intervalID, setIntervalID] = useState(0);
const handleStart = () => {
if (!intervalID) {
let interval = setInterval(() => setCount(prevCount => prevCount + 1), 1000);
setIntervalID(interval)
}
};
const handlePause = () => {
if (intervalID){
clearInterval(intervalID)
setIntervalID(0)
}
};
const handleStop = () => {
handlePause();
setCount(0)
};
const handleResume = () => {
handleStart();
};
return (
<div className="App">
<div className="counter">{count}</div>
<button onClick={handleStart} className="counter">
start
</button>
<button onClick={handleStop} className="counter">
stop
</button>
<button onClick={handlePause} className="counter">
pause
</button>
<button onClick={handleResume} className="counter">
resume
</button>
</div>
);
}
But this way, we have no way to clear the interval after unmounting the component. So we'll need useEffect(). And since we're using useEffect(), (check why here). And now, instead of saving our intervalID as the state, we can instead have an isRunning state and have useEffect create or clear the interval every time isRunning changes. So now all our handlers have to do is setIsRunning and useEffect will handle the rest.
So the code will look like this:
CodeSandbox
import "./styles.css";
import { useEffect, useState } from "react";
export default function App() {
const [count, setCount] = useState(0);
const [isRunning, setIsRunning] = useState(0);
useEffect(()=> {
let intervalId;
if (isRunning) {
intervalId = setInterval(() => setCount(prevCount => prevCount + 1), 1000);
} else {
clearInterval(intervalId)
}
return () => clearInterval(intervalId) // Clear after unmounting
}, [isRunning])
const handleStart = () => {
setIsRunning(true);
};
const handleStop = () => {
setIsRunning(false);
setCount(0)
};
const handlePause = () => {
setIsRunning(false);
};
const handleResume = () => {
handleStart();
};
return (
<div className="App">
<div className="counter">{count}</div>
<button onClick={handleStart} className="counter">
start
</button>
<button onClick={handleStop} className="counter">
stop
</button>
<button onClick={handlePause} className="counter">
pause
</button>
<button onClick={handleResume} className="counter">
resume
</button>
</div>
);
}
I really recommend you watch the talk I linked in the beginning. I'm sure you'll find it very helpful in terms of using hooks and some of the issues you can face and how to fix them.

clearInterval not working in React Application using functional component

I wanted to build a timer application in React using functional component and below are the requirements.
The component will display a number initialized to 0 know as counter.
The component will display a Start button below the counter number.
On clicking the Start button the counter will start running. This means the counter number will start incrementing by 1 for every one second.
When the counter is running(incrementing), the Start button will become the Pause button.
On clicking the Pause button, the counter will preserve its value (number) but stops running(incrementing).
The component will also display a Reset button.
On clicking the Reset button, the counter will go to its initial value(which is 0 in our case) and stops running(incrementing).
Below is the code that I have implemented, but clearInterval doesn't seems to be working, Also how do i implement Reset Button?
Code:
import React, { useState, useEffect } from "react";
export default function Counter() {
const [counter, setCounter] = useState(0);
const [flag, setFlag] = useState(false);
const [isClicked, setClicked] = useState(false);
var myInterval;
function incrementCounter() {
setClicked(!isClicked);
if (flag) {
myInterval = setInterval(
() => setCounter((counter) => counter + 1),
1000
);
setFlag(false);
} else {
console.log("sasdsad");
clearInterval(myInterval);
}
}
function resetCounter() {
clearInterval(myInterval);
setCounter(0);
}
useEffect(() => {
setFlag(true);
}, []);
return (
<div>
<p>{counter}</p>
<button onClick={incrementCounter}>
{isClicked ? "Pause" : "Start"}
</button>
<button onClick={resetCounter}>Reset</button>
</div>
);
}
Codesandbox link:
CodeSandbox

I did a slightly different version that use an extra useEffect that runs on isRunning (changed name from flag) change:
import React, { useState, useEffect, useRef } from "react";
export default function Counter() {
const [counter, setCounter] = useState(0);
// Change initial value to `false` if you don't want
// to have timer running on load
// Changed `flag` name to more significant name
const [isRunning, setIsRunning] = useState(false);
// You don't need 2 variable for this
//const [isClicked, setClicked] = useState(false);
// Using `useRef` to store a reference to the interval
const myInterval = useRef();
useEffect(() => {
// You had this line to start timer on load
// but you can just set the initial state to `true`
//setFlag(true);
// Clear time on component dismount
return () => clearInterval(myInterval.current);
}, []);
// useEffect that start/stop interval on flag change
useEffect(() => {
if (isRunning) {
myInterval.current = setInterval(
() => setCounter((counter) => counter + 1),
1000
);
} else {
clearInterval(myInterval.current);
myInterval.current = null;
}
}, [isRunning]);
// Now on click you only change the flag
function toggleTimer() {
setIsRunning((isRunning) => !isRunning);
}
function resetCounter() {
clearInterval(myInterval.current);
myInterval.current = null;
setCounter(0);
setIsRunning(false);
}
return (
<div>
<p>{counter}</p>
<button onClick={toggleTimer}>{isRunning ? "Pause" : "Start"}</button>
<button onClick={resetCounter}>Reset</button>
</div>
);
}
Demo: https://codesandbox.io/s/dank-night-wwxqz3?file=/src/Counter.js
As a little extra i've made a version that uses a custom hook useTimer. In this way the component code is way cleaner:
https://codesandbox.io/s/agitated-curie-nkjf62?file=/src/Counter.js

Use useRef to make the interval as a ref. Then use resetCounter() to clean the interval ref.
const intervalRef = useRef(null)
const incrementCounter = () => {
intervalRef.current = setInterval(() => {
setCounter(prevState => prevState + 1)
}, 1000);
};
const resetCounter = () => {
clearInterval(intervalRef.current);
intervalRef.current = null;
};

Between each rendering your variable myInterval value doesn't survive. That's why you need to use the [useRef][1] hook that save the reference of this variable across each rendering.
Besides, you don't need an flag function, as you have all information with the myClicked variable
Here is a modification of your code with those modifications. Don't hesitate if you have any question.
import React, { useState, useEffect, useRef } from "react";
export default function Counter() {
const [counter, setCounter] = useState(0);
const [isStarted, setIsStarted] = useState(false);
const myInterval = useRef();
function start() {
setIsStarted(true);
myInterval.current = setInterval(() => setCounter((counter) => counter + 1), 100);
100;
}
function pause() {
setIsStarted(false);
clearInterval(myInterval.current);
}
function resetCounter() {
clearInterval(myInterval.current);
setCounter(0);
}
return (
<div>
<p>{counter}</p>
{!isStarted ?
<button onClick={start}>
Start
</button>
:
<button onClick={pause}>
Pause
</button>
}
<button onClick={resetCounter}>Reset</button>
</div>
);
}
\\\
[1]: https://reactjs.org/docs/hooks-reference.html#useref

I'll just leave this here for anyone having the same problem.
in my case, the issue was node setInterval was used instead of window.setInterval.
this is a problem since this returns a type of Node.Timer which is an object instead of number (setInterval ID) for the clearInterval() to work as it needs an argument type of number. so to fix this,
React.useEffect(() => {
let timeoutId;
timeoutId = window.setInterval(callback, 100);
return = () => {
if(timeoutId) clearInterval(timeoutId)
}
}, [])
or in class components use componentWillMount()

You have to store myInterval in state. After that when button is clicked and flag is false, you can clear interval (myInterval in state).

SetInterval only run for first time

I learning javascript, react, and i tried to count from 10 to 0, but somehow the timer only run to 9, i thought setInterval run every n time we set (n can be 1000ms, 2000ms...)
Here is the code
import "./styles.css";
import React, { useState } from "react";
export default function App() {
const [time, setTime] = useState(10);
const startCountDown = () => {
const countdown = setInterval(() => {
setTime(time - 1);
}, 1000);
if (time === 0) {
clearInterval(countdown);
}
};
return (
<div>
<button
onClick={() => {
startCountDown();
}}
>
Start countdown
</button>
<div>{time}</div>
</div>
);
}
Here is the code:
https://codesandbox.io/s/class-component-ujc9s?file=/src/App.tsx:0-506
Please explain for this, i'm so confuse, thank you

time is the value read from the state (which is the default passed passed into useState) each time the component renders.
When you click, you call setInterval with a function that closes over the time that came from the last render
Every time the component is rendered from then on, it reads a new value of time from the state.
The interval is still working with the original variable though, which is still 10.
State functions will give you the current value of the state if you pass in a callback. So use that instead of the closed over variable.
setTime(currentTime => currentTime - 1);

Just use callback in your setState function because otherwise react is working with old value of time:
import "./styles.css";
import React, { useState } from "react";
export default function App() {
const [time, setTime] = useState(10);
const startCountDown = () => {
const countdown = setInterval(() => {
setTime((prevTime)=>prevTime - 1);
}, 1000);
if (time === 0) {
clearInterval(countdown);
}
};
return (
<div>
<button
onClick={() => {
startCountDown();
}}
>
Start countdown
</button>
<div>{time}</div>
</div>
);
}
edit: You can store your interval identificator in useRef, because useRef persist through rerender and it will not cause another rerender, and then check for time in useEffect with time in dependency
import "./styles.css";
import React, { useEffect, useRef, useState } from "react";
export default function App() {
const [time, setTime] = useState(10);
const interval = useRef(0);
const startCountDown = () => {
interval.current = setInterval(() => {
setTime((prevTime) => prevTime - 1);
}, 1000);
};
useEffect(() => {
if (time === 0) {
clearInterval(interval.current);
}
}, [time]);
return (
<div>
<button
onClick={() => {
startCountDown();
}}
>
Start countdown
</button>
<div>{time}</div>
</div>
);
}
working sandbox: https://codesandbox.io/s/class-component-forked-lgiyj?file=/src/App.tsx:0-613

How can I stop this recurstion function

import React, { useCallback, useState } from "react";
import { chat_chat } from "./chat_data.json"; // Length of the chat_chat array is over 10000
function App() {
const [slug, setSlug] = useState(0);
// const [stop, setStop] = useState(false);
// const stopFn = useCallback(() => {
// setStop(!stop);
// }, [stop]);
const slugAndURLImport = useCallback(() => {
let i = 0;
let stop = false;
const loopFn = () => {
setTimeout(() => {
console.log("stop", i, stop);
if (chat_chat.length < i || stop) {
return;
}
setSlug(chat_chat[i].slug);
i++;
loopFn();
}, 2000);
};
loopFn();
return () => {
stop = true;
};
}, []);
return (
<>
<div>
<button onClick={slugAndURLImport}> "Start" </button>
</div>
<div>{slug}</div>
<div>
<button
onClick={() => {
slugAndURLImport()();
}}>
Stop
</button>
</div>
</>
);
}
export default App;
Is there a way to stop the loopFn that is running?
loopFn is a function that imports data from arrays in json.
Or is there any other way than recursive function?
I want to stop the function when I press the button.
However, a new function starts and stops, and a function that is in progress does not stop.
Is there no way that javascript can stop the function in progress?
I'd like to use it in a react hooks.

You could use setInterval instead of a setTimeout in a recursive function. If you store the output of setInterval to a variable (maybe use a useRef hook) then you can call clearInterval to stop the loop.