Listening to Events in Hardhat using Ethers.js

This tutorial will help you with listening to Solidity smart contract events.

You can install Hardhat from here if you haven't already.

Step 1) Create a Hardhat Sample project with the following command

npx hardhat

To make life easy I will use the sample project provided by Hardhat for demonstrating events. Hopefully you can later use this example to add and listen to an event in your smart contract.

Note: Hardhat has upgraded since 2021 April, hence we get `lock.sol` contract by default instead of `greeter.sol` contract

Step 2) Create greeter.sol file and add an event to the contract as shown below

I know you are looking at console.log(), it is a fantastic feature provided by Hardhat but its topic for another day

We create an event named GreeterEvent() to log any change in the greeting message.

Step 3) Open a new terminal and start a Hardhat network on localhost

npx hardhat node

Step 4) Create a file name sample-script.js copy and paste the below code. Open another terminal and deploy your contract. The sample deploy script is already there for you

npx hardhat run --network localhost scripts/sample-script.js

Step 5) The main step — Connect with your smart contract and listen to events, here ethers.js library is used, refer to ethers lib for more details.
Hardhat is used for compiling, deploying, and testing your contract and Ethers is used to work with network providers, EVM, contracts and data regarding it.

Create a new file event.js in scripts folder as shown above.
I am really in love with Hardhat and ethers.js especially after looking at the ABI, thanks to RicMoo. The ABI is so much more readable and easy to understand than the provided standard.
I plan to create a tool for converting contract code to the above ABI format.

Make sure to add your contract address

let contractAddress = "your contract address";

Step 6) Run the script

npx hardhat run --network localhost scripts/event.js

Finally!!

You can see the result in your terminal

Lets add Filter to our event

Note: Hardhat has upgraded since 2021 April, so you can also refer: https://docs.ethers.io/v5/concepts/events/ for more info

To Filter the parameter we have to add the indexed keyword before the argument

pass the argument

Deploy the contract

npx hardhat run --network localhost scripts/sample-script.js

in event.js make changes to the ABI

Add the following lines to the end

Now you can filter the event as per the address of the greeting setter.

Hope this becomes a quick snippet for event listening.