Metamask: Setting array variable useState([]) in React.js returns undefined

Here’s an article about configuring the useState() array in React.js and how it relates to creating a Web3 dApp using MetaMask:

Setting up the StateuseState() array in React.js: a step-by-step guide

Introduction

———–

Creating a Web3 dApp using React.js can be a complex process, especially when it comes to interacting with the blockchain. One of the key features that makes Web3 dApps exciting is the ability to store and manage data on the blockchain. However, one of the common problems faced by many developers is setting the useState() array state variable in React.js.

In this article, we’ll look at how to configure the useState() array state variable in React.js and use it to create a basic Web3 dApp using MetaMask.

Initialize useState state variable

First, initialize the useState state variable. In our example, we will call it wallets'. We want this state variable to store an array of objects representing our wallet data.

import React, { useState } from 'react';
function App() {
const [wallets, setWallets] = useState([]);

• Reactis the main library for creating user interfaces in React.js.

• useStateis a function that allows us to initialize state variables. In this case, we use it to create an array state variable namedwallets.

• We pass an initial value of[], which means that our state variablewalletswill start with an empty array.

Now that we've initialized our state variable, let's use it in one of our React components. Let's call this componentWalletList.js.

import React, { useState } from 'react';
function WalletList() {
const [wallets, setWallets] = useState([]);
return (

Wallets




{wallets.map((wallet) => (
{wallet.address}
))}
);
}

• We initialized our walletsstate variable in theWalletListcomponent function usinguseState.

• We use themap()function to render a list of wallet objects. Each wallet object is rendered as a list item, and we pass thekey={wallet.id}property so that React can use it to identify each item.

Now that we've set up ourwalletsstate variable, let's create a basic Web3 dApp using MetaMask. We will use React's built-in Web3 library to interact with the blockchain.

import React, { useState } from 'react';
import Web3 from 'web3';
const web3 = new Web3(window.ethereum);
function App() {
const [wallets, setWallets] = useState([]);
return (

MetaMask Wallets
{wallets.map((wallet) => (
{wallet.address}
))}
 web3.eth.getBalance(wallets[0].address)}>Get Balance
);
}

• We are again using the map()` function to display the list of wallet objects, as before.

• We are adding two new buttons: one that gets the balance of the first wallet object, and another that displays all wallets.

That’s it! With this simple example, you should now have a useState() array state variable in React.js configured and used to create a Web3 dApp. Of course, there are still many features and complexities involved in building a real Web3 dApp, but hopefully this will give you a good starting point.

Note that this is only the tip of the iceberg. In this article, we only slightly touched on what is possible with React.js and Web3.

BENEFITS ANALYSIS TRADING