some-file.js

const fs = require('fs');
const { promisify } = require('util');
const hash = require('./hash');

const { dbs: dbsPath } = require('./paths');

const readFilePromise = promisify(fs.readFile);
const getDBFileContentsFromName = async name => readFilePromise(`${dbsPath}/${name}`, 'utf-8');

const getNodeContentsFromName = async name => getDBFileContentsFromName(`${name}.json`);

const getOriginHashFromFile = async () => getDBFileContentsFromName('origin-hash.txt');
const getLastHashFromFile = async () => getDBFileContentsFromName('last-hash.txt');

let originHash;
const setOriginHashFromFile = async () => {
  originHash = await getOriginHashFromFile();
};
setOriginHashFromFile();

const checkBlockHash = async (blockHash) => {
  const blockContent = await getNodeContentsFromName(blockHash);
  return hash.checkMatchesContent(blockHash, blockContent);
};
const checkBlockIntegrity = async (blockHash) => {
  if (!await checkBlockHash(blockHash)) {
    return false; 
  }

  // more code to appear here
};
const checkChainIntegrity = async () => {
  const lastBlockHash = await getLastHashFromFile();

  return checkBlockIntegrity(lastBlockHash);
};

// and still need to declare the exports