如何使用 useEffect 挂钩停止自动重新渲染组件？

Question

I am using useEffect hook and I have two states.
The two states depend on each other; which means that when I change one state basecurrency then the other state totalamount also gets updated and visa versa.

Each state has different functions that are called when states change.
Initially both states are set as value 0.

Challenge
Whenever the component is loaded, the page re-renders continously due to state changes and am not able to enter any input.

 useEffect(() => {
    getRequest("/user/get-user-details")
      .then(d => {
        if (d.code == 1) {
          localStorage.setItem("username", `${d.user.name}`);
          setuseremail(d.user.email);
          setusernumber(d.user.mobileNumber);

          postEwalletRequest("showEWalletBalance", {
            wallet_id: d.user.mobileNumber
          })
            .then(res => {
              console.log(res);
              if (res.status == 1) {
                setballance(res.data.balance);
              }
            })
            .catch(error => {
              console.log(error);
            });
    inclusiveTask();
    exclusiveTask();
  }, [basecurrency,totalamount]);

These are the functions:

const inclusiveTask=()=>{
  getRequest("/get-all-conversionPricelistforconsumer")
    .then(res => {
      setCurrList(res.saveConversionPriceList);
      setExchangeRate(res.saveConversionPriceList[0].amount);
      const converstionPrice = basecurrency * exchangeprice;
      // console.log("convert", converstionPrice);

      setconvertCurrency(converstionPrice);
      console.log("setconvertCurrency", convertcurrency);
      const Amount = `${
        converstionPrice - (converstionPrice * gatewaycharge) / 100
      }`;
      setTotalAmount(Amount);
      const transfee = Amount - converstionPrice;
      setChargeAmount(transfee);
      console.log("Amount", Amount);
      console.log("transfee", transfee);
    })
    .catch(error => {
      console.log(error);
    });

 }

const exclusiveTask = () => {
  getRequest("/get-all-conversionPricelistforconsumer")
   .then(res => {
     setCurrList(res.saveConversionPriceList);
     setExchangeRate(res.saveConversionPriceList[0].amount);
     const Extotal= totalamount/exchangeprice;//100cad
     console.log("Extotal", Extotal);
     const ExclufeeAmount = `${
       totalamount - (totalamount * gatewaycharge) / 100
     }`; //28500
     console.log("ExclufeeAmount", ExclufeeAmount);
     const excluService = totalamount -  ExclufeeAmount;//1500

     const extracharge = excluService / exchangeprice;//5
     console.log("extracharge", extracharge);

     const TotalExclusive = Extotal + extracharge;
     console.log("TotalExclusive", TotalExclusive);
     setCurrency(TotalExclusive);
    
   })
   .catch(error => {
     console.log(error);
   });
};

Please suggest any solution to help me fix this issue.

Answer 1

Simply you need to check is your values changed once, and if it was happen - use return statement to prevent looping. Also you can split your code in two separate useEffects to make it clear and easier to work with the code.

Here is some example:

Answer 2

I think you may be looking for a formulation like this, but it's really hard to tell from such a sprawling question.

The idea here is that

• getUserDetails returns a promise of user details
• getConversionPriceList returns a promise the price list data (that was previously in the inclusiveTask/exclusiveTask functions)
• inclusiveTask and exclusiveTask are simple non-async functions that just do maths

These are hooked up like so:

• the first useEffect has no dependencies, ie it's run exactly once, when the component mounts. It calls the user details and price functions and stores those bits in the state.
• the second useEffect is dependent on the user details and price lists, as well as the state for the base currency and amount (whatever those are, I don't know about your business logic). It has a guard to make it not do anything until the loading effects finish.
• The rendering simply says "Loading" until the required state is ready, and then it unceremoniously dumps the computation results as JSON (if any).

async function getUserDetails() {
  const d = await getRequest("/user/get-user-details");
  if (d.code !== 1) {
    return undefined;
  }
  localStorage.setItem("username", `${d.user.name}`);
  const retVal = {
    username: d.user.name,
    email: d.user.email,
    mobileNumber: d.user.mobileNumber,
    balance: undefined,
  };
  const res = await postEwalletRequest("showEWalletBalance", {
    wallet_id: d.user.mobileNumber,
  });
  if (res.status === 1) {
    retVal.balance = res.data.balance;
  }
  return retVal;
}

async function getConversionPriceList() {
  const res = await getRequest("/get-all-conversionPricelistforconsumer");
  return {
    currList: res.saveConversionPriceList,
    exchangeRate: res.saveConversionPriceList[0].amount,
  };
}

function inclusiveTask(basecurrency, exchangeprice, gatewaycharge) {
  const converstionPrice = basecurrency * exchangeprice;
  const Amount =
    converstionPrice - (converstionPrice * gatewaycharge) / 100;
  const transfee = Amount - converstionPrice;
  return { converstionPrice, Amount, transfee };
}

function exclusiveTask(totalamount, exchangeprice, gatewaycharge) {
  const Extotal = totalamount / exchangeprice; //100cad
  const ExclufeeAmount = totalamount - (totalamount * gatewaycharge) / 100; //28500
  const excluService = totalamount - ExclufeeAmount; //1500
  const extracharge = excluService / exchangeprice; //5
  const TotalExclusive = Extotal + extracharge;
  return {
    Extotal,
    ExclufeeAmount,
    excluService,
    extracharge,
    TotalExclusive,
  };
}

function MyComponent() {
  const [basecurrency, setBaseCurrency] = useState("USD");
  const [totalamount, setTotalAmount] = useState(0);
  const [userDetails, setUserDetails] = useState();
  const [prices, setPrices] = useState();
  const [results, setResults] = useState();

  useEffect(() => {
    // Need an IIFE here since `useEffect` can not return a promise
    (async () => {
      setUserDetails(await getUserDetails());
      setPrices(await getConversionPriceList());
    })();
  }, []);

  useEffect(() => {
    if (!(userDetails && prices)) {
      // Not ready to compute yet
      return;
    }
    setResults({
      inclusive: inclusiveTask(/* ... */),
      exclusive: exclusiveTask(/* ... */),
    });
  }, [prices, userDetails, basecurrency, totalamount]);
  if (results === undefined) {
    return <>Still loading...</>;
  }
  return <>{JSON.stringify(results)}</>;
}