Customer lookup

Take a look at the customer-lookup directory, https://github.com/PacktPublishing/Hands-on-JavaScript-for-Python-Developers/tree/master/chapter-11/customer-lookup, and run the script with node index.js. It's fairly simple:

const fs = require('fs')
const readline = require('readline')
 
const rl = readline.createInterface({
 input: process.stdin,
 output: process.stdout
});
 
const customers = []
 
getCustomers()
ask()
 
function getCustomers() {
 const files = fs.readdirSync('data')
 
 for (let i = 0; i < files.length; i++) {
   const data = fs.readFileSync(`data/${files[i]}`)
   customers.push(JSON.parse(data))
 }
}
 
function ask() {
 rl.question(`There are ${customers.length} customers. Enter a number to 
 see details:\n`, (customer) => {
   if (customer > customers.length || customer < 1) {
     console.log("Customer not found. Please try again")
   } else {
     console.log(customers[customer - 1])
   }
   ask()
 })
}

Some of this will...