Trying to understand if I always need to identify commonjs or module?

{
  "name": "incoming-mobile-event-service",
  "version": "1.0.15",
  "description": "ES6 RESTful Express API for SOME SERVICE",
  "main": "dist",
  "scripts": {
    },
  "eslintConfig": {
    "extends": "eslint:recommended",
    "parserOptions": {
      "ecmaVersion": 7,
      "sourceType": "module"
    },
    "env": {
      "node": true,
      "es6": true
    },
    "rules": {
      "no-console": 1,
      "no-unused-vars": 1
    }
  },
  "repository": "https://gitlab.com/COMPANYDev/COMPANY-DEPT/SOME-service",
  "author": "COMPANY IT",
  "dependencies": {
   },
  "devDependencies": {
  }
}

import bodyParser from 'body-parser';
import express from 'express';
import validator from 'express-validator';
import http from 'http';
import morgan from 'morgan';
import swagger from 'swagger-ui-express';

import config from './config.json';
import swaggerConfig from './config/swagger.json';
import winston from './config/winston';
import tracing from './config/tracing';
import {
  defaultNotFoundHandler,
  defaultErrorHandler,
} from './controllers/error.controller';
import { checkDatabaseConnections } from './config/health';

var os = require('os');