SignTypedDataVector.js

const { ethers } = require("ethers");
const sigUtil = require('@metamask/eth-sig-util');

// The wallet to sign with
const hdWallet = ethers.utils.HDNode.fromMnemonic('all all all all all all all all all all all all').derivePath(ethers.utils.defaultPath)
const privateKey = Buffer.from(hdWallet.privateKey.substr(2), 'hex')

msgParams = {
    domain: {
      // Defining the chain aka Rinkeby testnet or Ethereum Main Net
      chainId: 1,
      // Give a user friendly name to the specific contract you are signing for.
      name: 'Ether Mail',
      // If name isn't enough add verifying contract to make sure you are establishing contracts with the proper entity
      verifyingContract: '0xCcCCccccCCCCcCCCCCCcCcCccCcCCCcCcccccccC',
      // Just let's you know the latest version. Definitely make sure the field name is correct.
      version: '1',
    },

    // Defining the message signing data content.
    message: {
      /*
       - Anything you want. Just a JSON Blob that encodes the data you want to send
       - No required fields
       - This is DApp Specific
       - Be as explicit as possible when building out the message schema.
      */
      contents: 'Hello, Bob!',
      attachedMoneyInEth: 4.2,
      from: {
        name: 'Cow',
        wallets: [
          '0xCD2a3d9F938E13CD947Ec05AbC7FE734Df8DD826',
          '0xDeaDbeefdEAdbeefdEadbEEFdeadbeEFdEaDbeeF',
        ],
      },
      to: [
        {
          name: 'Bob',
          wallets: [
            '0xbBbBBBBbbBBBbbbBbbBbbbbBBbBbbbbBbBbbBBbB',
            '0xB0BdaBea57B0BDABeA57b0bdABEA57b0BDabEa57',
            '0xB0B0b0b0b0b0B000000000000000000000000000',
          ],
        },
      ],
    },
    // Refers to the keys of the *types* object below.
    primaryType: 'Mail',
    types: {
      // TODO: Clarify if EIP712Domain refers to the domain the contract is hosted on
      EIP712Domain: [
        { name: 'name', type: 'string' },
        { name: 'version', type: 'string' },
        { name: 'chainId', type: 'uint256' },
        { name: 'verifyingContract', type: 'address' },
      ],
      // Not an EIP712Domain definition
      Group: [
        { name: 'name', type: 'string' },
        { name: 'members', type: 'Person[]' },
      ],
      // Refer to PrimaryType
      Mail: [
        { name: 'from', type: 'Person' },
        { name: 'to', type: 'Person[]' },
        { name: 'contents', type: 'string' },
      ],
      // Not an EIP712Domain definition
      Person: [
        { name: 'name', type: 'string' },
        { name: 'wallets', type: 'address[]' },
      ],
    },
  }

const version = sigUtil.SignTypedDataVersion.V4

async function main() {
  console.log("Signing with", hdWallet.address)

  console.log("Signature", await sigUtil.signTypedData({
    data: msgParams,
    version: version,
    privateKey: privateKey
  }))

  const { domain, types, primaryType, message } =
    sigUtil.TypedDataUtils.sanitizeData(msgParams)

  const domainSeparatorHex = sigUtil.TypedDataUtils.hashStruct(
    'EIP712Domain',
    domain,
    types,
    version,
  ).toString('hex');

  const hashStructMessageHex = sigUtil.TypedDataUtils.hashStruct(
    primaryType,
    message,
    types,
    version
  ).toString('hex');

  console.log("domain separator hash:", domainSeparatorHex)
  console.log("message hash:", hashStructMessageHex)
}

main()
  .then(() => process.exit(0))
  .catch((error) => {
    console.error(error);
    process.exit(1);
  });