CosignAuthorityProvider.js

// A custom cosigner AuthorityProvider for EOSJS v2
// This provider overrides the checks on all keys,
// allowing a partially signed transaction to be
// broadcast to the API node.

const { convertLegacyPublicKeys } = require('eosjs/dist/eosjs-numeric');

module.exports = class CosignAuthorityProvider {

  constructor(rpc) {
    this.actor = 'energytester';
    this.permission = 'active';
    this.rpc = rpc;
  }
  
  async getRequiredKeys(args) {
    
    const { transaction } = args;

    // Iterate over the actions and authorizations
    transaction.actions.forEach((action, ti) => {
      action.authorization.forEach((auth, ai) => {
        // If the authorization matches the expected cosigner
        // then remove it from the transaction while checking
        // for what public keys are required
        if (
          auth.actor === 'energytester'
          && auth.permission === 'active'
        ) {
          delete transaction.actions[ti].authorization.splice(ai, 1)
        }
      })
    });

    // the rpc below should be an already configured JsonRPC client from eosjs
    return convertLegacyPublicKeys((await this.rpc.fetch('/v1/chain/get_required_keys', {
      transaction,
      available_keys: args.availableKeys,
    })).required_keys);
  }

}