server.js

var express     = require('express'),
    bodyParser  = require('body-parser'),
    fs          = require('fs'),
    app         = express(),
    customers   = JSON.parse(fs.readFileSync('data/customers.json', 'utf-8')),
    orders      = JSON.parse(fs.readFileSync('data/orders.json', 'utf-8')),
    states      = JSON.parse(fs.readFileSync('data/states.json', 'utf-8'));

app.use(bodyParser.urlencoded({ extended: true }));
app.use(bodyParser.json());

//Would normally copy necessary scripts into src folder (via grunt/gulp) but serving
//node_modules directly to keep everything as simple as possible
app.use('/node_modules', express.static(__dirname + '/node_modules')); 

//The src folder has our static resources (index.html, css, images)
app.use(express.static(__dirname + '/src')); 

app.get('/api/customers', (req, res) => {
    res.json(customers);
});

app.get('/api/customers/:id', (req, res) => {
    let customerId = +req.params.id;
    let selectedCustomer = {};
    for (let customer of customers) {
        if (customer.id === customerId) {
           selectedCustomer = customer;
           break;
        }
    }  
    res.json(selectedCustomer);
});

app.post('/api/customers', (req, res) => {
    let postedCustomer = req.body;
    let maxId = Math.max.apply(Math,customers.map((cust) => cust.id));
    postedCustomer.id = ++maxId;
    postedCustomer.gender = (postedCustomer.id % 2 === 0) ? 'female' : 'male';
    customers.push(postedCustomer);
    res.json({ status: true });
});

app.put('/api/customers/:id', (req, res) => {
    let putCustomer = req.body;
    let id = +req.params.id;
    let status = false;
    for (let i=0,len=customers.length;i<len;i++) {
        if (customers[i].id === id) {
            customers[i] = putCustomer;
            status = true;
            break;
        }
    }
    res.json({ status: status });
});

app.delete('/api/customers/:id', function(req, res) {
    let customerId = +req.params.id;
    for (let i=0,len=customers.length;i<len;i++) {
        if (customers[i].id === customerId) {
           customers.splice(i,1);
           break;
        }
    }  
    res.json({ status: true });
});

app.get('/api/orders', function(req, res) {
    res.json(orders);
});

app.get('/api/orders/:id', function(req, res) {
    let customerId = +req.params.id;
    for (let order of orders) {
        if (order.customerId === customerId) {
            return res.json([ order ]);
        }
    }
    res.json([]);
});

app.get('/api/states', (req, res) => {
    res.json(states);
});

// redirect all others to the index (HTML5 history)
app.all('/*', function(req, res) {
    res.sendFile(__dirname + '/src/index.html');
});

app.listen(3000);

console.log('Express listening on port 3000.');

//Open browser
var opn = require('opn');

opn('http://localhost:3000').then(() => {
    console.log('Browser closed.');
});