Cant update value of state using custom hooks

Question

I created a custom hook which contains four states. then I imported that hook into two functional components. then I was updating one of the state in the second component. but the state doesnt changed in the first component.

import React , {useState} from "react"

/** Custom hook component **/
const useApp = () => {
    const[millisec , setMillisec] = useState(0)
    const[sec , setSec] = useState(0)
    const[min , setMin] = useState(0)
    const[hr , setHr] = useState(0)

    return {millisec , setMillisec , sec , setSec , min , setMin , hr , setHr}
    
}

export default useApp;

/** First JS FIle **/

import React from "react"
import useApp from "../App"
import Interact from "./Interact";

const Timer = () => {
    
    
    const {millisec  , sec  , min  , hr } = useApp();

    return(
        <>
             <div>{hr}</div>
            <div>{min}</div>
            <div>{sec}</div>
            <div>{millisec}</div>
            <Interact />
        </>
    )
}
export default Timer

/** SECOND JS FILE **/

import React from "react"
import useApp from "../App"


const Interact = () => {

    const {millisec , setMillisec , sec , setSec , min , setMin , hr , setHr} = useApp();

    const handleStart = () => {
        setMillisec(prev => prev +1)
        
    return(
        <>
        <button onClick = {handleStart}>Start</button>
        <p>{millisec}</p>
        </>
    )
}

export default Interact

I could Change the initial state value millisec in the second.js file and in custom hook file but i want to change the value of millisec in first js file as the state get changed when i click the Start button

Answer 1

Just pass it down:

const Timer = () => {
    const { millisec, setMillisec, sec  , min  , hr} = useApp();

   const handleStart = () => {
       setMillisec(prev => prev + 1)
   }

    return(
        <>
             <div>{hr}</div>
            <div>{min}</div>
            <div>{sec}</div>
            <div>{millisec}</div>
            <Interact handleStart={handleStart} millisec={millisec} />
        </>
    )
}