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

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Here’s an article on setting up an array usestate () in react.js and how it relates to creating a web3 dapp using metamask:

Setting up an array stateusestate () 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 common challenge that many developers face is setting up an array state usestate () variable in react.js.

In this article, we’ll explore how to set an array state usestate () variable in react.js and use it to create a basic web3 dapp using metamask.

initializing the usestate state variable

First, let’s initialize the usestate state variable. In our example, we’ll call it wallets. We want this state variable to store an array of objects that represent our wallet data.

JSX

Import react, {usestate} from ‘react’;

Function App () {

Const [wallets, suwallets] = usestate ([]);

HERE’S What’s Happening:

React is the main library for building user interfaces in react.js.

usestate is a function that allows us to initialize state variables. In this case, we're using it to create an array state variable calledwallets.

We pass the initial value of[], which means ourWalletsState variable will start with an empty array.



 Using usestate state variable in a component

Now that we have initialized our state variable, let's use it in one of our react components. Let's call this componentWalletlist.js.

JSX

Import react, {usestate} from ‘react’;

Function Walletlist () {

Const [wallets, suwallets] = usestate ([]);

return (

Wallets

{wallets.map ((wallet) => (

{wallet.address}

))}

);

}

HERE’S What’s Happening:

We’ve initialized our state variable Wallets in the component’sWalletlist 'Function UsingUsestate.

We're using themap ()Function to render a list of wallet objects. Each wallet object is rendered as a list item, and we're passing thekey = {wallet.id}Prop so that react can use it to identify each item.



 Creating A Web3 Dapp

Now that we have set up our state variableWallets, let's create a basic web3 dapp using metamask. We'll use react's built-in web3 library to interact with the blockchain.

JSX

Import react, {usestate} from ‘react’;

Import Web3 from ‘Web3’;

Const Web3 = New Web3 (Window.ethereum);

Function App () {

Const [wallets, suwallets] = usestate ([]);

return (

Metamask Wallets

{wallets.map ((wallet) => (

{wallet.address}

))}

);

}

HERE’S What’s Happening:

We’re using the web3 library to get an instance of the Ethereum provider. We step in our metamask wallet address as a parameter.

We’re using the Map () Function Again to render a list of wallet objects, just like before.

We’re 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 basic example, you should now have an array state usestate () variable in react.js set up and using it to create a web3 dapp. Of course, there are many more features and complexities involved in creating a real-world Web3 dapp, but hopefully this gives you a good starting point.

Note that this is just the kind of the iceberg. In this article, we’ve only scratched the surface of what’s possibly with react.js and web3.

Wallets

Metamask Wallets

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