How to Mint & Burn an ERC-721 Token Using Hardhat and Ethers (Part 1)

In this tutorial, you'll learn how to deploy, mint, and burn ERC-721 tokens (NFTs) using Hardhat, Ethers, and OpenZeppelin contracts on the Hedera Testnet. We'll cover setting up your project, writing and deploying an ERC-721 smart contract, minting an NFT to your account, and finally, burning an NFT.

By the end, you'll have hands-on experience with essential ERC-721 operations and interacting with smart contracts on Hedera.

You can take a look at the complete code in the Hedera-Code-Snippets repository.

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Prerequisites

• Basic understanding of smart contracts.

• Basic understanding of Node.js and JavaScript.

• Basic understanding of Hardhat Ethereum Development Tool and Ethers.

• ECDSA account from the Hedera Portal.

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Table of Contents

1. Project Setup

   1. Initialize Project

   2. Create .env File

   3. Configure Hardhat

2. Creating the ERC-721 Contract

3. Deploy Your Smart Contract

4. Minting an NFT

5. Adding the Burn Functionality

6. Burning an NFT

Step 1: Project Setup

Initialize Project

Set up your Node.js project by initializing npm:

npm init -y

Install Dependencies

Next, install the required dependencies:

npm install @openzeppelin/contracts dotenv

We also need a bunch of developer dependencies to be able to deploy and interact with smart contracts through Hardhat:

npm install --save-dev @nomicfoundation/hardhat-toolbox

Create .env File

To create your .env file, you can either run one of the following commands or simply rename the .env.example file in the project's root directory:

option 1: create a new .env file

touch .env

option 2: duplicate the .env.example file

cp .env.example .env

Securely store your sensitive data like the OPERATOR_KEY in a .env file. For the JSON RPC_URL, we'll use the Hashio RPC endpoint for testnet.

.env

OPERATOR_KEY=your-operator-key
RPC_URL=https://testnet.hashio.io/api

Replace the your-operator-key environment variable the HEX Encoded Private Key for your ECDSA account from the Hedera Portal.

Please note: that Hashio is intended for development and testing purposes only. for production use cases, it's recommended to use commercial-grade JSON-RPC Relay or host your own instance of the Hiero JSON-RPC Relay.

Configure Hardhat

Create a hardhat.config.jsfile in the root of your project. This file contains the network settings so Hardhat knows how to interact with the Hedera Testnet. We'll use the variables you've stored in your .env file.

hardhat.config.js

require("dotenv").config();
require("@nomicfoundation/hardhat-toolbox");

module.exports = {
  solidity: {
    version: "0.8.22",
  },
  defaultNetwork: "testnet",
  networks: {
    testnet: {
      // HashIO RPC testnet endpoint in the .env file
      url: process.env.RPC_URL,
      // Your ECDSA account private key pulled from the .env file
      accounts: [process.env.OPERATOR_KEY],
    }
  }
};

You can verify the connection by running:

npx hardhat console --network testnet

This command launches an interactive JavaScript console connected directly to the Hedera Testnet, providing access to the Ethers.js library for blockchain interactions. If you successfully enter this interactive environment, your Hardhat configuration is correct. To exit the interactive console, press ctrl + c twice.

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Step 2: Creating the ERC-721 Contract

Create a new Solidity file (erc-721.sol ) in a new contracts directory:

erc-721.sol

// SPDX-License-Identifier: MIT
// Compatible with OpenZeppelin Contracts ^5.0.0
pragma solidity ^0.8.22;

import {ERC721} from "@openzeppelin/contracts/token/ERC721/ERC721.sol";
import {Ownable} from "@openzeppelin/contracts/access/Ownable.sol";

contract MyToken is ERC721, Ownable {
    uint256 private _nextTokenId;

    constructor(address initialOwner)
        ERC721("MyToken", "MTK")
        Ownable(initialOwner)
    {}

    function safeMint(address to) public onlyOwner returns (uint256) {
        uint256 tokenId = _nextTokenId++;
        _safeMint(to, tokenId);
        return tokenId;
    }
}

This contract was created using the OpenZeppelin Contracts Wizard and OpenZeppelin's ERC-721 standard implementation with an ownership model. The ERC-721 token's name has been set to "MyToken." The contract implements the safeMint function, which accepts the address of the owner of the new token and uses auto-increment IDs, starting from 0.

Let's compile this contract by running:

npx hardhat compile

This command will generate the smart contract artifacts, including the ABI. We are now ready to deploy the smart contract.

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Step 3: Deploy Your ERC-721 Smart Contract

Create a deployment script (deploy.js) in a new scripts directory:

deploy.js

async function main() {
  // Get the signer of the tx and address for minting the token
  const [deployer] = await ethers.getSigners();
  console.log("Deploying contracts with the account:", deployer.address);

  // The deployer will also be the owner of our NFT contract
  const MyToken = await ethers.getContractFactory("MyToken", deployer);
  const contract = await MyToken.deploy(deployer.address);

  console.log("Contract deployed at:", contract.target);
}

main().catch(console.error);

In this script, we first retrieve your account (the deployer) using Ethers.js. This account will own the deployed smart contract. Next, we use this account to deploy the contract by calling MyToken.deploy(deployer.address). This passes your account address as the initial owner and signer of the deployment transaction.

Deploy your contract by executing the script:

npx hardhat run scripts/deploy.js --network testnet

Copy the deployed address—you'll need this in subsequent steps.

The output looks like this:

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Step 4: Minting an NFT

Create a mint.js script in your scripts directory to mint an NFT. Don't forget to replace the <your-contract-address> with the address you've just copied.

mint.js

async function main() {
    const [deployer] = await ethers.getSigners();
    
    // Get the ContractFactory of your MyToken ERC-721 contract
    const MyToken = await ethers.getContractFactory("MyToken", deployer);
    
    // Connect to the deployed contract 
    // (REPLACE WITH YOUR CONTRACT ADDRESS)
    const contractAddress = "<your-contract-address>";
    const contract = await MyToken.attach(contractAddress);
    
    // Mint a token to ourselves
    const mintTx = await contract.safeMint(deployer.address);
    const receipt = await mintTx.wait();
    const mintedTokenId = receipt.logs[0].topics[3];
    console.log('Minted token ID:', mintedTokenId);
    
    // Check the balance of the token
    const balance = await contract.balanceOf(deployer.address);
    console.log('Balance:', balance.toString(), "NFTs");
}

main().catch(console.error);

The code mints a new NFT to your account ( deployer.address ). Then we verify the balance to see if we own an ERC-721 token of type MyToken.

Mint an NFT:

npx hardhat run scripts/mint.js --network testnet

Expected output:

Minted token ID: 0x0000000000000000000000000000000000000000000000000000000000000000 // Represents ID 0
Balance: 1 NFT

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Step 5: Adding the Burn Functionality

Update your contract to add NFT burning capability by importing the burnable extension and adding it to the interfaces list for your contract:

// [...]
import {ERC721Burnable} from "@openzeppelin/contracts/token/ERC721/extensions/ERC721Burnable.sol";

contract MyToken is ERC721, ERC721Burnable, Ownable {
// [...]

Recompile and redeploy:

npx hardhat compile
npx hardhat run scripts/deploy.js --network testnet

Copy the new smart contract address and replace the address in the scripts/mint.js script with your new address. Let's mint a new NFT for the redeployed contract:

npx hardhat run scripts/mint.js --network testnet

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Step 6: Burning an NFT

Create a burn script (burn.js ) in your scripts directory:

burn.js

async function main() {
    const [deployer] = await ethers.getSigners();
    const MyToken = await ethers.getContractFactory("MyToken", deployer);
    
    // Connect to the deployed contract (REPLACE WITH YOUR CONTRACT ADDRESS)
    const contractAddress = "<your-contract-address>";
    const contract = await MyToken.attach(contractAddress);
    
    // Burn the token
    const burnTx = await contract.burn(0);
    await burnTx.wait();
    console.log('Burned token with ID:', 0);
    
    // Check the balance of the token
    const balance = await contract.balanceOf(deployer.address);
    console.log('Balance:', balance.toString(), "NFTs");
}

main().catch(console.error);

Again, ensure you update <your-contract-address> to interact with your correct contract. The script will burn the ERC-721 token with the ID set to 0, which is the ERC-721 token you've just minted. To be sure the token has been deleted, let's print the balance for our account to the terminal. The balance should show a balance of 0.

Burn the NFT:

npx hardhat run scripts/burn.js --network testnet

Congratulations! 🎉 You have successfully learned how to deploy an ERC-721 smart contract using Hardhat, OpenZeppelin, and Ethers. Feel free to reach out in Discord!

Additional Resources

• OpenZeppelin ERC-721 Documentation

• Hedera Smart Contracts Workshop

• Full Code in Hedera-Code-Snippets Repository

Writer: Michiel, Developer Relations Engineer

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Editor: Luis, Sr Software Developer

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Editor: Krystal, Technical Writer

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