some-file.js

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

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

class MahClass {
  constructor() {
    this.readFilePromise = promisify(fs.readFile);
    this.originPath = this.getOriginHashFromFile();
  }
  
  getDBFileContentsFromName(name) {
    return this.readFilePromise(`${dbsPath}/${name}`, 'utf-8'); 
  }

  getNodeContentsFromName(name) {
    return this.getDBFileContentsFromName(`${name}.json`); 
  }
  
  getOriginHashFromFile() {
    return this.getDBFileContentsFromName('origin-hash.txt'); 
  }

  getLastHashFromFile() {
    return this.getDBFileContentsFromName('last-hash.txt');
  }
  
  setOriginHashFromFile() {
    this.originHash = this.getOriginHashFromFile(); 
  }
  
  checkBlockHash(blockHash) {
    const blockContent = this.getNodeContentsFromName(blockHash);
    return hash.checkMatchesContent(blockHash, blockContent);
  }
  
  checkBlockIntegrity(blockHash) {
    if(!this.checkBlockHash(blockHash)) {
      return false;
    }
    
    // more code to appear here
  }
  
  checkChainIntegrity() {
    const lastBlockHash = this.getLastHashFromFile();
    return this.checkBlockIntegrity(lastBlockHash);
  }
  
  
}

// and still need to declare the exports