How to Use a Signer in Ethers.js

What is a Signer in ethers.js?

A Signer is an abstraction to the Ethereum Account that has access to a private key, which grants access to messages and transactions to be securely signed off-chain while maintaining an interaction with the blockchain.

A Signer allows you to verify that you own a particular account, so that you can send transactions to the blockchain from that account.

Ethers.js Signer Use Cases

The following are four potential use cases of a Signer within Ethers.js:

• Balances - use signer.getBalance to retrieve the balance of a user’s wallet
• ENS Domains - use signer.resolveName to retrieve the ENS domain connected to the wallet address.
• Signing - use signer.signTransaction to sign a transaction to confirm ownership by a specific wallet address.
• Wallet - use ethers.Wallet to create a new wallet by passing in a private key identifying the owner of the wallet.

There are many more use cases that can be explored by visiting the Signer docs, here.

How to Use a Signer with the Alchemy SDK

This example will teach you how to send a transaction using the Alchemy SDK. Please Note: The following code snippets require prior installation of alchemy-SDK.

1. Import Alchemy, Network, Wallet and Utils via alchemy-sdk. Learn more about dotev, here.

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const { Alchemy, Network, Wallet, Utils } = require("alchemy-sdk");
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const dotenv = require("dotenv");

2. Optional Config object, but defaults to demo api-key and eth-mainnet.

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const { API_KEY, PRIVATE_KEY } = process.env;
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const settings = {
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    apiKey: API_KEY,
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    network: Network.ETH_GOERLI, // Replace with your network.
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};
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const alchemy = new Alchemy(settings);

3. Define wallet - an implementation of Signer that can sign transactions and messages using a private key.

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let wallet = new Wallet(PRIVATE_KEY);

4. Define the transaction and specify details required of the transaction.

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const transaction = {
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    to: "0xa238b6008Bc2FBd9E386A5d4784511980cE504Cd",
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    value: Utils.parseEther("0.001"),
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    gasLimit: "21000",
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    maxPriorityFeePerGas: Utils.parseUnits("5", "gwei"),
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    maxFeePerGas: Utils.parseUnits("20", "gwei"),
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    nonce: await alchemy.core.getTransactionCount(wallet.getAddress()),
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    type: 2,
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    chainId: 5, // Corresponds to ETH_GOERLI
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};

5. Define the raw transaction using wallet and transact using Alchemy’s API methods.

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const rawTransaction = await wallet.signTransaction(transaction);
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await alchemy.transact.sendTransaction(rawTransaction);