Overview

Ethers.js is a powerful library for interacting with the Ethereum blockchain, but there are common pitfalls that developers may encounter. Understanding these pitfalls can help you avoid issues and build more robust decentralized applications (dApps). Below are some common mistakes to watch out for when using Ethers.js.

1. Not Handling Promises Properly

Many Ethers.js functions return promises, and failing to handle them correctly can lead to unhandled promise rejections. Always use async/await or .then() to handle promises.

        
            // Incorrect: Not handling the promise
            const provider = new ethers.providers.JsonRpcProvider(process.env.RPC_URL);
            provider.getBlockNumber(); // This will not work as expected

            // Correct: Using async/await
            async function getBlockNumber() {
                const blockNumber = await provider.getBlockNumber();
                console.log(blockNumber);
            }
            getBlockNumber();
            

2. Hardcoding Private Keys

Never hardcode private keys directly in your code. This exposes your keys to anyone who has access to your source code. Instead, use environment variables or secure vaults.

        
            // Incorrect: Hardcoding private key
            const wallet = new ethers.Wallet("YOUR_PRIVATE_KEY"); // DO NOT DO THIS

            // Correct: Using environment variables
            const wallet = new ethers.Wallet(process.env.PRIVATE_KEY);
            

3. Ignoring Gas Fees

When sending transactions, always consider gas fees. Failing to set an appropriate gas limit or gas price can result in failed transactions or excessive costs.

        
            const tx = {
                to: "0xRecipientAddress",
                value: ethers.utils.parseEther("0.1"),
                gasLimit: 21000, // Set an appropriate gas limit
                gasPrice: ethers.utils.parseUnits("10", "gwei") // Set gas price
            };

            const transactionResponse = await wallet.sendTransaction(tx);
            await transactionResponse.wait();
            

4. Not Validating User Input

Always validate user input to prevent errors and potential security vulnerabilities. For example, ensure that Ethereum addresses are valid before using them.

        
            const address = "0xInvalidAddress";

            // Incorrect: Not validating the address
            const balance = await provider.getBalance(address); // This will throw an error

            // Correct: Validating the address
            if (ethers.utils.isAddress(address)) {
                const balance = await provider.getBalance(address);
                console.log(balance.toString());
            } else {
                console.error("Invalid address");
            }
            

5. Forgetting to Wait for Transaction Confirmation

When sending transactions, it's important to wait for confirmation to ensure that the transaction has been mined. Failing to do so can lead to unexpected behavior.

        
            const tx = await wallet.sendTransaction({
                to: "0xRecipientAddress",
                value: ethers.utils.parseEther("0.1")
            });

            // Incorrect: Not waiting for confirmation
            console.log("Transaction sent:", tx.hash);

            // Correct: Waiting for confirmation
            const receipt = await tx.wait();
            console.log("Transaction confirmed in block:", receipt.blockNumber);
         

6. Not Using the Correct Network

Ensure that you are connected to the correct Ethereum network (mainnet, testnet, etc.) when deploying contracts or sending transactions. Using the wrong network can lead to lost funds or failed transactions.

        
            const provider = new ethers.providers.JsonRpcProvider("https://mainnet.infura.io/v3/YOUR_INFURA_PROJECT_ID");

            // Incorrect: Using the wrong network
            const wrongProvider = new ethers.providers.JsonRpcProvider("https://ropsten.infura.io/v3/YOUR_INFURA_PROJECT_ID");

            // Correct: Ensure you are on the right network
            const correctProvider = new ethers.providers.JsonRpcProvider("https://mainnet.infura.io/v3/YOUR_INFURA_PROJECT_ID");
            

Conclusion

By being aware of these common pitfalls when using Ethers.js, you can avoid potential issues and build more secure and efficient decentralized applications. Always handle promises properly, protect sensitive information, and validate user input to ensure a smooth development experience.