What is Ethers.js?

Ethers.js is a powerful JavaScript library that allows developers to interact with the Ethereum blockchain. It provides a simple API for tasks such as sending transactions, reading data from smart contracts, and connecting to various Ethereum networks, including test networks.

What are Test Networks?

Test networks (or testnets) are Ethereum networks that allow developers to test their applications without using real Ether. They provide a safe environment to experiment with smart contracts and transactions. Common Ethereum test networks include:

  • Ropsten: A proof-of-work test network that closely resembles the Ethereum mainnet.
  • Rinkeby: A proof-of-authority test network that is more stable than Ropsten.
  • Kovan: Another proof-of-authority test network with a focus on speed.

Connecting to a Test Network

To connect to a test network using Ethers.js, you can use the getDefaultProvider method, which automatically selects a suitable provider for the specified network. Below is an example of how to connect to the Rinkeby test network.

1. Set Up Your Project

If you haven't set up an Ethers.js project yet, you can follow these steps: 

mkdir ethers-testnet-project
cd ethers-testnet-project
npm init -y
npm install ethers

2. Create an HTML File

Create an index.html file in your project directory. You can use the following code as a starting point: 

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Connect to Test Network with Ethers.js</title>
    <script src="https://cdn.jsdelivr.net/npm/ethers@5.7.0/dist/ethers.umd.min.js"></script>
</head>
<body>
    <h1>Connect to Rinkeby Test Network</h1>
    <button id="getBlockButton">Get Latest Block</button>
    <pre id="blockInfo"></pre>
    <script>
        async function connectToRinkeby() {
            // Create a default provider for the Rinkeby test network
            const provider = ethers.getDefaultProvider("rinkeby");
            
            // Get the latest block
            const blockNumber = await provider.getBlockNumber();
            const block = await provider.getBlock(blockNumber);
            document.getElementById('blockInfo').innerText = JSON.stringify(block, null, 2);
        }

        document.getElementById('getBlockButton').onclick = connectToRinkeby;
    </script>
</body>
</html>

3. Run a Local Server

To view your project in a browser, you’ll need to serve it over a local server. You can use a simple server like http-server or any other static server. Install it globally using npm if you haven't already: 

npm install -g http-server

Then, run the server in your project directory: 

http-server

Open your browser and navigate to http://localhost:8080 (or the port shown in your terminal) to see your application in action.

Conclusion

Connecting to a test network using Ethers.js is straightforward. By using the getDefaultProvider method, you can easily interact with test networks like Rinkeby, allowing you to test your Ethereum applications without the risk of using real Ether. This setup is essential for developers looking to build and test decentralized applications effectively.