Dynamically load express routes from subfolder

app.js

/* main express file: app.js */
const express = require('express')
const app = express()
// other middleware 
require('./routes')(app)

index.js

/* routes folder: routes/index.js */
const { readdirSync } = require('fs')

module.exports = app => {
  readdirSync(__dirname).forEach(file => {
    if (file === 'index.js') return
    const route = file.split('.')[0]
    require(`./${route}`)(app)
  })
}

user.js

/* routes folder: routes/user.js */
module.exports = app =>{
  app.get('/api/getUser', (req, res) => {
    // ....
  })
  app.post('/api/postUser', (req, res) => {
  // ....
  })
}