react pomodoro like timer with setInterval - reactjs

Question

The Idea is - I press 'start timer' and a function sets the variable 'sessionSeconds' based on whether its work 25mins or rest 5mins session (true/false). Problem is , when interval restarts, function doesn't update this 'currentSessionSeconds'. Maybe it's something with lifecycles or I should use useEffect somehow..
const TimeTracker = () => {
const [work, setWork] = useState(25);
const [rest, setRest] = useState(5);
const [remainingTime,setRemainingTime]= useState(25);
const [iswork, setIswork] = useState(true);
function startTimer() {
clearInterval(interval);
let sessionSeconds = iswork? work * 60 : rest * 60
interval = setInterval(() => {
sessionSeconds--
if (duration <= 0) {
setIswork((iswork) => !iswork)
updateTime(sessionSeconds)
startTimer();
}
}, 1000);
function updateTime(seconds){
setRemainingTime(seconds)
}
}
return (
<div>
<p>
{remainingTime}
</p>
<button onClick={startTimer}>timer</button>
</div>
);
}
I didnt include other code for converting, etc to not over clutter.

Answer 1

I couldn't get your code working to test it since it is missing a }.
I changed your code to include use effect and everything seems to work fine.
https://codesandbox.io/s/wizardly-saha-0dxde?file=/src/App.js
const TimeTracker = () => {
/* In your code you used use state however you didn't change
the state of these variables so I set them to constants.
You can also pass them through props.
*/
const work = 25;
const rest = 5;
const [remainingTime, setRemainingTime] = useState(work * 60);
const [isWork, setIsWork] = useState(true);
const [isTimerActive, setIsTimerActive] = useState(false);
const startTimerHandler = () => {
isWork ? setRemainingTime(work * 60) : setRemainingTime(rest * 60);
setIsTimerActive(true);
};
useEffect(() => {
if (!isTimerActive) return;
if (remainingTime === 0) {
setIsWork((prevState) => !prevState);
setIsTimerActive(false);
}
const timeOut = setTimeout(() => {
setRemainingTime((prevState) => prevState - 1);
}, 1000);
/* The return function will be called before each useEffect
after the first one and will clear previous timeout
*/
return () => {
clearTimeout(timeOut);
};
}, [remainingTime, isTimerActive]);
return (
<div>
<p>{remainingTime}</p>
<button onClick={startTimerHandler}>timer</button>
</div>
);
};