vote-sign.js

const createVoteBySigMessage = (govAddress, proposalId, support, chainId = 1) => {
  const types = {
    EIP712Domain: [
      { name: 'name', type: 'string' },
      { name: 'chainId', type: 'uint256' },
      { name: 'verifyingContract', type: 'address' },
    ],
    Ballot: [
      { name: 'proposalId', type: 'uint256' },
      { name: 'support', type: 'uint8' }
    ]
  };

  const primaryType = 'Ballot';
  const domain = { name: 'Compound Governor Bravo', chainId, verifyingContract: govAddress };
  support = support.toString();
  const message = { proposalId, support };

  return JSON.stringify({ types, primaryType, domain, message });
};