Learn HARDHAT with Real Code Examples

// contracts/Counter.sol
pragma solidity ^0.8.0;

contract Counter {
    uint256 public count = 0
    function increment() public { count += 1 }
}

// scripts/deploy.js
async function main() {
    const [deployer] = await ethers.getSigners()
    const Counter = await ethers.getContractFactory('Counter')
    const counter = await Counter.deploy()
    await counter.deployed()
    console.log('Counter deployed to:', counter.address)
}

main().catch((error) => { console.error(error); process.exitCode = 1 })

A minimal example showing how to deploy a simple smart contract using Hardhat scripts.

async function main() {
    const [deployer] = await ethers.getSigners()
    const Counter = await ethers.getContractFactory('Counter')
    const counter = await Counter.attach('0xYourContractAddress')
    await counter.increment()
    const value = await counter.count()
    console.log('Counter value:', value)
}

main().catch((error) => { console.error(error); process.exitCode = 1 })

Call a deployed smart contract function using Hardhat runtime environment.

async function main() {
    const accounts = await ethers.getSigners()
    accounts.forEach((account, i) => console.log(`Account ${i}: ${account.address}`))
}

main().catch((error) => { console.error(error); process.exitCode = 1 })

Retrieve and display the list of accounts provided by Hardhat network.

async function main() {
    const Counter = await ethers.getContractFactory('Counter')
    const counter = await Counter.attach('0xYourContractAddress')
    const gasEstimate = await counter.estimateGas.increment()
    console.log('Estimated gas:', gasEstimate)
}

main().catch((error) => { console.error(error); process.exitCode = 1 })

Estimate gas for a contract method call using Hardhat.

// contracts/Greeting.sol
pragma solidity ^0.8.0;

contract Greeting {
    string public message
    constructor(string memory _msg) { message = _msg }
}

// scripts/deploy.js
async function main() {
    const Greeting = await ethers.getContractFactory('Greeting')
    const greeting = await Greeting.deploy('Hello Hardhat')
    await greeting.deployed()
    console.log('Greeting deployed at:', greeting.address)
}

main().catch((error) => { console.error(error); process.exitCode = 1 })

Deploy a contract with constructor parameters using Hardhat.

async function main() {
    const Counter = await ethers.getContractFactory('Counter')
    const counter = await Counter.attach('0xYourContractAddress')
    counter.on('Incremented', (newValue) => {
        console.log('Counter incremented to:', newValue)
    })
}

main().catch((error) => { console.error(error); process.exitCode = 1 })

Listen to events emitted by a contract using Hardhat provider.

async function main() {
    const Counter = await ethers.getContractFactory('Counter')
    const counter = await Counter.attach('0xYourContractAddress')
    const value = await counter.count()
    console.log('Counter value:', value)
}

main().catch((error) => { console.error(error); process.exitCode = 1 })

Read a public variable from a deployed contract using Hardhat.

async function main() {
    const [sender, receiver] = await ethers.getSigners()
    const tx = await sender.sendTransaction({ to: receiver.address, value: ethers.parseEther('1') })
    await tx.wait()
    console.log('Ether transferred')
}

main().catch((error) => { console.error(error); process.exitCode = 1 })

Send Ether from one account to another on Hardhat local network.

async function main() {
    const Counter = await ethers.getContractFactory('Counter')
    const counter = await Counter.deploy()
    await counter.deployed()
    const Greeting = await ethers.getContractFactory('Greeting')
    const greeting = await Greeting.deploy('Hi there')
    await greeting.deployed()
    console.log('Contracts deployed')
}

main().catch((error) => { console.error(error); process.exitCode = 1 })

Deploy multiple contracts sequentially in Hardhat script.

const { upgrades } = require('hardhat')
async function main() {
    const Counter = await ethers.getContractFactory('Counter')
    const counter = await upgrades.deployProxy(Counter, [0])
    await counter.deployed()
    console.log('Upgradeable Counter deployed at:', counter.address)
}

main().catch((error) => { console.error(error); process.exitCode = 1 })

Deploy an upgradeable contract using Hardhat and OpenZeppelin upgrades plugin.