We will learn how to create your own ERC-20 token and deploy it to a live testnet and deploy the react frontend to vercel.

Code is available at Github, demo at https://erc20-hardhat-waffle-react.vercel.app/

This project uses open-zeppelin for smart contracts, hardhat, ethers for interacting with blockchain and waffle for writing tests and typescript, react for frontend, for UI we will use a UI library called baseweb to get us started quickly.

The whole process is broken down into

1. Setup
2. Writing code
3. Testing with hardhat local blockchain
4. Deploying contract to Rinkeby testnet
5. Deploying the frotend to vercel

1. Setup

Run npm init and initialise your your package.json

hardhat & waffle: npm install --save-dev @nomiclabs/hardhat-ethers @nomiclabs/hardhat-waffle hardhat ethers ethereum-waffle chai

TypeScript: npm install --save-dev typescript ts-node @types/react @types/node @types/mocha Typechain: npm install --save-dev ts-generator typechain @typechain/ethers-v5 @typechain/hardhat

npm install --force --save-dev hardhat-typechain, we use force because theres an issue with version conflicts with typechain

Baseweb: npm install --save baseui styletron-react styletron-engine-atomic

Others: npm install --save-dev dotenv

React: npm install --save react react-dom react-scripts

SmartContracts: npm install --save @openzeppelin/contracts

After installing all the above dependencies setup your hardhat.config.ts by running npx hardhat. I'd suggest you copy hardhat and typescript from the code's github repo to get started quickly

---

2. Code

Token.sol in /contracts/ folder

//SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC20/ERC20.sol";

contract Token is ERC20 {
    constructor(string memory name, string memory symbol) ERC20(name, symbol) {
        _mint(msg.sender, 100000 * (10 ** uint256(decimals())));
    }
}

This is our contract which creates 100,000 Tokens with the name and symbol that we will provide while deploying the contract. We are inheriting from the open-zeppelin ERC20 contract which has alot of inbuilt methods which you can check here

Now run npx hardhat compile, this step will generate our typechain types for our contracts and compile the solidity smart contract and create solidity ABI's in a folder src/artifacts which we will import in our react code to interact with our contract

You should find them here /artifacts/contracts/Token.sol/Token.json

Fronend code to interact with our contract

import Token from './artifacts/contracts/Token.sol/Token.json';
import React, { useState, useEffect } from 'react';
import { ethers } from 'ethers';
...

const tokenAddress = "0xCB1B15E3d881E7F9Bc05a7eFc61efE9661C112cb"
const DECIMALS = 18;
const NETWORK = 'rinkeby';

function App(props) {
  const [css, theme] = useStyletron();
  const [contract, setContract] = useState(null);
  const [balance, setBalance] = useState();
  const [account, setAccount] = useState(null);
  const [supply, setSupply] = useState(0);

  const [accountBalance, setAccountBalance] = useState(0);
  const [allowance, setAllowance] = useState(0);
  const [showLoader, setShowLoader] = useState(true);

  useEffect(async () => {
    if (typeof window.ethereum !== 'undefined') {
      const [account] = await window.ethereum.request({ method: 'eth_requestAccounts' })
      const provider = new ethers.providers.Web3Provider(window.ethereum);
      const network = await provider.getNetwork();
      if(network.name !== NETWORK) {
        return alert("Connect to rinkeby test net to connect to the contract");
      }

      const signer = provider.getSigner();
      const contract = new ethers.Contract(tokenAddress, Token.abi, provider);
      const contractWithSigner = contract.connect(signer);

    ...
    }
  }, [])

  const getBalance = async () => {
    const balance = await contract.balanceOf(account);
    const tokensInContract = formatEther(balance)
    setBalance(tokensInContract);
  }

    ...

  return (
    <div className={["App", css({backgroundColor: "#f9e47d"})].join(' ')}>
      <Container>    
        <h1>Yoga Coin</h1>            
        {showLoader ? <Spinner /> : 
          <>                        
            <p>💰 Total Token Supply: {supply}</p>
            <p>📨 Contract Address: {contract.address}</p>
            <p>📨 User Address: {account}</p>     
            <div className={css({display: "flex", flexDirection: "column"})}>
              <p>💰 User Balance: {balance}</p>
              <Button onClick={getBalance}>Get Balance</Button>
            </div> 
          </>
        }
      </Container>
    </div>
  );
}

In our react code, we are importing the contract ABI, connecting to the metamask's network which is injected into the browser as window.ethereum. We use ethers.js library to connect to metamask. The provider contains network info and signer contains the user's account info like address.

We connect to the contract using const contract = new ethers.Contract(tokenAddress, Token.abi, provider); and run methods on the contract to perform various actions like transferring, approving tokens and checking balance. Check the code in App.js to see how all the functions like balance, approve, transfer, allowance are implemented.

---

3. Deploy and Test in local hardhat node

Open a new terminal window and run npx hardhat node to run hardhat's local network, this command also generates 20 usable public-private key pairs of which the first pair is used to deploy our contract.

To deploy our contract to hardhat's local network, we first create a folder called scripts and write a deploy.js script in it.

Deploy script

const hre = require("hardhat");

async function main() {
  const [deployer] = await hre.ethers.getSigners();

  console.log(
    "Deploying contracts with the account:",
    deployer.address
  );

  const Token = await hre.ethers.getContractFactory("Token");
  const YogaCoin = await Token.deploy("YogaCoin", "YOGA");

  await YogaCoin.deployed();

  console.log("Token deployed to:", YogaCoin.address);
}

main()
  .then(() => process.exit(0))
  .catch(error => {
    console.error(error);
    process.exit(1);
  });

This is a typical hardhat deploy script which we can use to deploy our Token contract. Notice we are initialising our contract with a name and symbol, which are YogaCoin and YOGA. Lets assume that user with these coins can get access to special yoga classes which teachers can accept.

In the above code, hre.ethers.getSigners() returns the signer object of the account connected to hardhat config's default blockchain network. In this case its the first account generated by hardhat when the blockchain node is created.

Once the contract is deployed you can see the address of the deployed contract.

Now place this contract address in the tokenAddress variable in App.js to connect our frontend to the contract in our local hardhat node.

Now to test the contract, add the network details in your metamask

Now in an other terminal window while the node is running, run npm run start and make sure you have react-scripts start in your scripts field in package.json. Now head to http://localhost:3000 to interact with the contract, make sure you are connected to the Localhost Hardhat node network in your metamask wallet

---

4. Deploying contract to Rinkeby testnet

Deploying contracts costs eth gas, so we acquire test ether from Rinkeby's faucet here. Make sure your metamask account is connected to Rinkeby Test network and check if it has some ether in it.

Also we create a project in Infura get an infura api key to interact and create contracts in rinkeby network

Then create a .env file in your repo and add the following keys to it, make sure .env is file added in your .gitignore so that you wont accidentally upload your private key details to github.

INFURA_API_KEY=** INFURA PROJECT API KEY**
RINKEBY_PRIVATE_KEY=** YOUR PRIVATE KEY OF YOUR METAMASK ACCOUNT ** 

Make sure you use a test eth account's private key.

Then we modify our hardhat.config.js to make rinkeby as our default network

const RINKEBY_PRIVATE_KEY =
  process.env.RINKEBY_PRIVATE_KEY ||
  "0xc87509a1c067bbde78beb793e6fa76530b6382a4c0241e5e4a9ec0a0f44dc0d3"; // well known private key


const config: HardhatUserConfig = {
  defaultNetwork: "rinkeby",
  solidity: "0.8.0",
...
  networks: {
    hardhat: {
      chainId: 1337 // TO WORK WITH METAMASK
    },
    localhost: {},
    rinkeby: {
      url: `https://rinkeby.infura.io/v3/${INFURA_API_KEY}`,
      accounts: [RINKEBY_PRIVATE_KEY],
    },

  }
};

Done, now we deploy our contract to the rinkeby network using the same deploy command we used before: npx hardhat run scripts/deploy.js --network rinkeby

You can see the address where our contract is deployed. To confirm it, lets head to etherscan and paste our contract address in the search bar.

You should find the contract deployed on etherscan, with the tokens name, owner, balance etc..

Now there's an important step here which is to place this contract address in our frontend App.js so that we are connecting to the right contract. So in App.js, make sure you have the new contract address assigned to tokenAddress variable const tokenAddress = "0xCB1B15E3d881E7F9Bc05a7eFc61efE9661C112cb"

---

5. Deploying front-end to vercel.

Before we deploy our frontend to vercel, create an account in vercel.com and connect your github account to it. It allows you to import your repos from github and deploy automagically to a subdomain on vercel.com

Add the following to your package.json for the vercel build step to succeed

  "scripts": {
    "start": "react-scripts start",
    "build": "react-scripts build",
    "compile": "npx hardhat compile",
    "test": "npx hardhat test"
  },

Now in your vercel dashboard, click import project, select your repo and click deploy. Vercel will install all the dependencies, build and deploy your project and gives you the final public deploy url. Visit the url to finally interact with your contract.

This demo is hosted here at https://erc20-hardhat-waffle-react.vercel.app/