index.js

var express = require('express');
const path = require('path');
var morgan = require('morgan')

var app = express();
const createPath = (page) => path.resolve(__dirname, 'views', `${page}.ejs`)

app.set('view engine', 'ejs');

app.use(morgan('combined'));
app.use(express.json());
app.use('/img', express.static('web/img'));
app.use('/css', express.static('web/css'));
app.use('/js', express.static('web/js'));
app.use('/build', express.static('node_modules'));

app.get('/', function(req, res) {
    const title = 'Главная';
    res.render(createPath('index'), { title });
});

app.get('/diagram', function(req, res){
    const title = 'Редактор диаграмм';
    res.render(createPath('diagram'), { title });
});

app.use((req, res) => {
    const title = 'Ошибка 404';
    res.render(createPath('404'), { title });
});

app.listen(8081);