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Prerequisites

1

Node.js Installed

Ensure you have Nodejs installed on your system. You can download it from Node.js’ official website.
2

API Key and Mnemonic

Obtain an API key from the dev portal Ensure you have a valid Ethereum mnemonic phrase of the account with a signer associated with the above API key.
3

Dependencies Installed

Install the required packages:
yarn add siwe viem @neynar/nodejs-sdk

​
Code Breakdown and Steps

1

Import Required Libraries

The code begins by importing the necessary libraries:
import { SiweMessage } from "siwe";
import { mnemonicToAccount } from "viem/accounts";
import { NeynarAPIClient, Configuration } from "@neynar/nodejs-sdk";
2

Define Your Mnemonic

Replace "YOUR_MNEMONIC_HERE" with your Ethereum mnemonic phrase:
const mnemonic = "YOUR_MNEMONIC_HERE";
3

Convert Mnemonic to Account

The mnemonicToAccount function converts your mnemonic into an account object:
const account = mnemonicToAccount(mnemonic);
4

Configure Neynar API Client

Replace "YOUR_API_KEY_HERE" with your API key and set the correct base path for the Neynar API:
const config = new Configuration({
  apiKey: "YOUR_API_KEY_HERE",
});

const client = new NeynarAPIClient(config);
5

Create the SIWE Message

The createSiweMessage function generates a SIWE message with details such as domain, address, and nonce:
async function createSiweMessage(address, statement) {
  const { nonce } = await client.fetchNonce();

  const message = new SiweMessage({
    scheme: "http",
    domain: "localhost:8080",
    address,
    statement,
    uri: "http://localhost:8080",
    version: "1",
    chainId: "1",
    nonce: nonce,
  });

  return message.prepareMessage();
}
6

Sign and Verify the Message

The fetchSigners function handles the signing process and fetches signers:Note: The address should be the custody_address of the farcaster account (Check custody_address in User API)
async function fetchSigners() {
  const address = account.address;

  let message = await createSiweMessage(
    address,
    "Sign in with Ethereum to the app."
  );

  const signature = await account.signMessage({ message });

  const { signers } = await client.fetchSigners({ message, signature });

  return signers;
}
7

Execute the Function

Call the fetchSigners function and handle success or errors:
fetchSigners()
  .then((signers) => {
    console.log("\n\nsigners:", signers, "\n\n");
  })
  .catch((error) => {
    console.error("error:", error);
  });

​
Expected Output

[
  {
    "object": "signer",
    "signer_uuid": "19d0c5fd-9b33-4a48-a0e2-bc7b0555baec",
    "public_key": "0xe4abc135d40f8a6ee216d1a6f2f4e82476dff75f71ea53c5bdebca43f5c415b7",
    "status": "approved",
    "fid": 0
  },
  {
    "object": "signer",
    "signer_uuid": "08c71152-c552-42e7-b094-f510ff44e9cb",
    "public_key": "0xe4cd577123def73295dd9991c589b59b48cdc976b5e83a9ad8d2a13fcfcc0e72",
    "status": "approved",
    "fid": 0
  }
]
For additional help, feel free to contact us.