What is Hardhat?

• Hardhat is a development environment to compile, deploy, test, and debug your Ethereum software. If you were using remix so far, everything was pretty straightforward. But once you move into actual development, there's a high probability you won't use remix.

• It's written in Javascript Language.

• Why would you choose Hardhat against Truffle?

• By faster migration I mean faster deployment on your Ethereum network.

• fewer gas fees are consumed during the deployment process.

• Debugging is easy, that's pretty much straightforward.

Installing Hardhat.

• Well, first you'll need the package.json file so npm init --yes
• Now, install the hardhat file. npm i --save-dev hardhat
• Now, to setup the folder structure run the following command. npx hardhat

• select > Create an empty hardhat.config.js prompt.

• on selecting it, a file called hardhat.config.js will be created.

• update the module.exports = {solidity: "0.8.8"} -> to the appropriate solidity version.

• Create the following folders.

• "contracts/" => you'll store your contracts here.

• "test/" => you'll create your test scripts.

• "scripts" => your deployment scripts will be saved here.

• Now, we'll install our test libraries to run tests on our contracts.

• npm i --save-dev @nomiclabs/hardhat-ethers ethers @nomiclabs/hardhat-waffle ethereum-waffle chai

the hardhat.config.js file is the entry point for hardhat. We now require the following to use it in the file.

//imports
require("@nomiclabs/hardhat-waffle")

Compiling in Hardhat.

Now that we have installed hardhat in our system, let's understand how to compile the solidity code. npx hardhat compile.

• after we compile the following solidity file, an abi, as well as a bytecode file, is created.

Testing our compiled contract.

To test our contract we use our previously installed library called mocha.

• create a file in the test folder having the name of the solidity file you want to test.

const {ethers} = require("hardhat");
const {expect,assert} = require ("chai") 

describe("Test for  SimpleStorage", ()=>{

let simpleStorageFactory,simpleStorage


// we run beforeEach before every it
  beforeEach(async () => {

    //simpleStorage is the solidity file.
    simpleStorageFactory = await ethers.getContractFactory("SimpleStorage");

    simpleStorage = await simpleStorageFactory.deploy()

 })

//test condition that's executed
it("Should Start with 0", async function () {
  const currentValue = await simpleStorage.retrieve()
  const expectedValue = "0"

 assert.equal(currentValue.toString(),expectedValue)
}

})

• describe() is a function that hardhat and mocha will understand, it takes 2 parameters

• hardhat test uses the mocha framework, which is the javascript framework used to test our code.

• We run these test by using the following cmd

• npx hardhat test to run all the tests

• npx hardhat test --grep string this string is searched in all first parameters of it()

Debugging in Hardhat.

How do we add javascript code within our solidity code? import "hardhat/console.sol". within the solidity file. console.log("SENDER BALANCE",balance[msg.sender]);

Deploying to a live network

Now, in the scripts/ folder, create a deploy.js folder.

//require
const {ethers} = require('hardhat');

//main()
async function main(){
  const contractFactory = await ethers.getContractFactory("solidityFile");
  //*  Now we deploy the contract
  const contractStorage = await lockStorageFactory.deploy();
//* now we wait for it to deploy on the network
  await contractStorage.deployed()
}

//function call
main()
.then(()=>process.exit(0))
.catch((e)=>{console.log(e);process.exit(1);})

now lets run the contract npx hardhat run scripts/deploy.js

• you can also deploy on other networks.
• To do that first, you need to set up the PRIVATE_KEY and well as the PRC_URL on the hardhat.config.js file

module.exports = {
  defaultNetword: "hardhat",
      networks: {
          rinkeby:{
            url: process.env.RINKEBY_PRC_URL,
           accounts:[process.env.PRIVATE_KEY],
           chainId: 4,  
      }
  }
}

now to deploy on the rinkeby network run the following hardhat run scripts/deploy.js --network rinkeby

Interacting with the contract

• We can call our abis just as a normal function associated with the contract object. eg. retrieve() and store()

• in the main function

const currentValue = await contractStorage.retrieve();
//* Initial Value
console.log(`current value: ${currentValue}`);

const currentValue = await contractStorage.store(7);

const currentValue = await contractStorage.retrieve();
//* after store function is called.
console.log(`current value: ${currentValue}`);

• The moment you run the npx hardhat run .\scripts\deploy.js command you'll see the values in the prompt.