Smart Contracts With Hardhat

❖ Create a project folder such as "hello_world" and run "npm init -y" as follows (in macOS)...

mkdir hello_world ↩️
cd hello_world ↩️
npm init -y ↩️

When using "npm", you need to install "Node.js" first.

"-y" which means to use the default basic configuration information of the system when the project is initialized.

❖ Then you need to install Hardhat package in the hello_world project folder as follows...

npm install --save-dev hardhat ↩️

❖ After the installation is complete, you can enter the following command to see the installed files.

ls -a ↩️ 

.                 node_modules      package.json
..                package-lock.json

❖ Run "npx hardhat" as follows...

npx hardhat ↩️ 

choose " Create an empty hardhat.config.js "  ↩️

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888    888                      888 888               888
8888888888  8888b.  888d888 .d88888 88888b.   8888b.  888888
888    888     "88b 888P"  d88" 888 888 "88b     "88b 888
888    888 .d888888 888    888  888 888  888 .d888888 888
888    888 888  888 888    Y88b 888 888  888 888  888 Y88b.
888    888 "Y888888 888     "Y88888 888  888 "Y888888  "Y888

👷 Welcome to Hardhat v2.9.9 👷‍

? What do you want to do? …
  Create a JavaScript project
  Create a TypeScript project
❯ Create an empty hardhat.config.js
  Quit

❖ Install the openzeppelin and other packages in the hello_world project folder as follows...

npm install --save-dev @openzeppelin/hardhat-upgrades ↩️

npm install --save-dev @nomiclabs/hardhat-ethers ethers ↩️

npm install --save-dev @nomiclabs/hardhat-waffle ↩️

npm install @openzeppelin/contracts ↩️

❖ Install the Dotenv package as follows...

npm install dotenv ↩️

❖ Create a .env file as follows...

❖ Open .env file and enter a the environment variable as follows...

PRIVATE_KEY=YOUR_PRIVATE_KEY

❗️❗️❗️ "YOUR_PRIVATE_KEY" can be obtained in your MetaMask.

❖ Open your hardhat.config.js file and add code as follows...

require("@nomiclabs/hardhat-waffle");
require('@openzeppelin/hardhat-upgrades');

require('dotenv').config();

/** @type import('hardhat/config').HardhatUserConfig */
module.exports = {
  solidity: "0.8.17",
  networks:{
    goerli:{
      url : `https://goerli.infura.io/v3/YOUR-API-KEY`,
      accounts: [`0x${process.env.PRIVATE_KEY}`]
    }
  }
};

❗️❗️❗️ "YOUR-API-KEY", Because we are using "Goerli test network ", so you need create a project in "app.infura.io" before you can get the api_key.

❗️❗️❗️ How to check your "Goerli test network" information as follows...

❖ Create a "contracts" folder and "hello_world.sol" file in the hello_world project folder.

mkdir contracts ↩️
cd contracts ↩️
touch hello_world.sol ↩️

❖ Open the "hello_world.sol" file and add code as follows... 

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.9;

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

contract hello_world_token is ERC20, Ownable {
    constructor() ERC20("hello_world_token", "H_W_TK") {
        _mint(msg.sender, 1000 * 10 ** decimals());
    }

    function mint(address to, uint256 amount) 
    public onlyOwner {
        _mint(to, amount);
    }
}

❗️❗️❗️ Contract full name   : "hello_world_token".
❗️❗️❗️ Contract symbol name : "H_W_TK".

❖ Compile your contract "hello_world.sol" as follows...

❗️❗️❗️ Back into your project root directory.

cd .. ↩️
npx hardhat compile ↩️

Compiled 6 Solidity files successfully

❖ Create a "scripts" folder and a "deploy.js" file in the hello_world project folder as follows...

mkdir scripts ↩️
cd scripts ↩️
touch deploy.js ↩️

❖ Open the "deploy.js" file and add code as follows...

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

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

    const weiAmount = (await deployer.getBalance())
        .toString();

    console.log("Account balance:",
        (await ethers.utils.formatEther(weiAmount)));

    // your ERC-20 contract name : hello_world_token
    const Token =
        await ethers
            .getContractFactory("hello_world_token");
    const token =
        await Token.deploy();

    // show your the token address in console window
    console.log("Token address:", token.address);
}

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

❖ Save and close the "deploy.js" file.
❖ Back into your project root directory.
❖ Run "npx hardhat run scripts/deploy.js --network goerli".

❗️❗️❗️ Need to pay Transaction Fee, so first you need to get Goerli's ETH before you deploy. You can get it for free at
https://goerlifaucet.com/.

cd .. ↩️
npx hardhat run scripts/deploy.js --network goerli ↩️

❖ If successful, you will see results as follows...

❖ Copy your "Token address :" number
e.g."0xC3E85411B6C734244CB41C40594c85292f63C4a8"

❖ Login your MetaMask and choose "Goerli test network".

❖ Paste your "Token address" to the "Token contract address" field and click the "Add custom token".

🎉 Congratulations finally finished.