.then() is not returning a promise-CodePudding

I am trying to import a function from another file and while rendering in the react component, it doesn't get rendered. The value of that variable is showing undefined

index.js

const GetOwnBalance = async () => {
    if (!isInitialized) {
        await init();
    }
    // const web2 = new Web3(provider);
    nftContract.methods
    .getBalance(selectedAccount)
        .call()
        .then((balance) => {
            // console.log(`Balance of ${selectedAccount} is ${balance}`);
            console.log("Intermediate balance : "   balance);
            // return balance;
        }   
    );
};
export default GetOwnBalance;

Until this everything runs perfect, but the problem is in App.js

App.js

import React, { useState } from 'react';
import  GetOwnBalance  from './index';

function App() {
    const [balance, setBalance] = useState(0);
    function fetchBalance() {
        GetOwnBalance()
            .then(value => {
                setBalance(value); //value shows undefined ???
                console.log("Final Balance : "   value);
            }
                
            );
    }

    return (
        <div className="App">
            <p>Your balance is {balance}</p>
            <button onClick={fetchBalance}>Refresh balance</button>
        </div>
    );
}

export default App;

When I try to run this piece of code, the value value in the .then() promise shows undefined. Can someone please explain why is it so?

CodePudding user response：

It is because you are not returning anything from function GetOwnBalance.

Try adding the return keyword in return nftContract.methods....

const GetOwnBalance = async () => {
    if (!isInitialized) {
        await init();
    }
    // const web2 = new Web3(provider);
   return nftContract.methods
    .getBalance(selectedAccount)
        .call()
        .then((balance) => {
            // console.log(`Balance of ${selectedAccount} is ${balance}`);
            console.log("Intermediate balance : "   balance);
            // return balance; <-- Also uncomment this
        }   
    );
};
export default GetOwnBalance;

CodePudding user response：

Is the "GetOwnBalance" function located at index.js or ./Web3Client'?

Instead of "value" parameter on

 .then(value => {
            setBalance(balance); //value shows undefined ???
            console.log("Final Balance : "   balance);
        }

Try just using the hook value name:

 .then(() => {
            setBalance(value);
            console.log("Final Balance : "   value);
        })

Additionally you don't have to set "GetOwnBalance" as async if you don't use await