React hook for using Timer with Milliseconds

useTimer.ts

import { useState, useRef } from "react";

const Timer = ( initial: number, ascending: boolean) => {
    const [ms, setMs] = useState(initial * 100)
    const [timesUp, setTimesUp] = useState<boolean>(false)
    const intervalRef = useRef<number>()
      
      
    function convertMSTimeToString (ms: number){
        const minutes = String(Math.floor( ms / 100 / 60)).padStart(2, '0')
        const seconds = String(Math.floor( (ms / 100) % 60 )).padStart(2, '0')
        const milliseconds = String(Math.floor(ms % 100)).padStart(2, '0')

        const timerString = `${minutes}:${seconds}:${milliseconds}`

        return {
            minutes,
            seconds,
            milliseconds,
            timerString
        }
    }
    
    function stopTimer() {
        window.clearInterval(intervalRef.current)        
    }
    
    function startTimer() {
        let intervalId = window.setInterval(() => {
            setMs( (prev) => {
                if (!ascending && prev === 0) {
                    stopTimer()
                    return prev
                } else {
                    return ascending ? prev + 1 : prev - 1
                }
            })
        }, 10)

        intervalRef.current = intervalId
    }

    function resetTimer() {
        setMs(initial)
    }

    let { minutes, seconds, milliseconds, timerString} = convertMSTimeToString(ms)
    return { minutes, seconds, milliseconds, timerString, timesUp, stopTimer, startTimer, resetTimer }
}

export default Timer