Basic Node and Express

Question 1

Create express app object(requiring express module & calling express function)

Answer 1

-npm install express
-const express = require(‘express’);
-const app = express();

Question 2

Structure for routes in express

Answer 2

app.METHOD(PATH(server-relative),HANDLER);

Question 3

Types of Methods

Answer 3

GET, POST, PUT, DELETE, OPTIONS, LISTEN, HEAD

Question 4

What is PATH

Answer 4

A URL pattern or endpoint relative to the server’s domain where the handler function should be executed

Question 5

What is Handler

Answer 5

A function handling the route when a specific route is matched during incoming HTTP request

Question 6

What form does the handler take

Answer 6

function(request, response){…}

Question 7

What do route handlers do?

Answer 7

Provide the core functionality for defining the behavior of your web application’s endpoints

Question 8

Give example of where route handler goes:

Answer 8

app.get(‘/endpoint’, function(req, res) {
//route handler here
res.send(‘this is the endpoint route’)
});

Question 9

What are 2 ways to Serve a HTML file:

Answer 9

-express.static middleware
-res.sendFile() METHOD

Question 10

Show how to serve static files from a directory(e.g ‘public’)

Answer 10

app.use(express.static(‘public’));

Question 11

When is express.static used

Answer 11

serving multiple static files(e.g HTML, CSS, Javascript)

Question 12

Show route handler for serving an HTML file with res.sendFile():

Answer 12

app.get(‘/page’, function(req, res){
res.sendFile(__dirname + ‘/public/page.html’);
});

‘/page’ = desired route path
‘/public/page.html’ = file relative to your project directory

Question 13

When to use res.sendFile()

Answer 13

Useful for serving specific files or for adding additional logic before sending the files

Question 14

What are middlewares?

Answer 14

-is software logic that intercepts and processes HTTP requests and responses within the application’s request-response cycle. It can modify request and response objects, execute additional code, or terminate the request cycle.
-Are functions that intercept route handlers, adding some kind of information.
-Has access to the request object(‘req’), the response object(‘res’), and the next middleware function in the application’s request-response cycle.
-Can execute code, make changes to the request and response objects, end the request-response cycle, or call the next middlewware function.

Question 15

what method does middlewares need to be mounted on?

Answer 15

app.use(…);

Question 16

Show how middleware would be executed for a certain request:

Answer 16

app.use(path, middlewareFunction)

Question 17

Show how middleware will be executed for all requests:

Answer 17

app.use(middlewareFunction)

Question 18

Common directory names for static assets:

Answer 18

‘public’, ‘static’, ‘assets’

Question 19

How to access static assets in the browser, assuming your server is running on port 3000:

Answer 19

http://localhost:3000/index.html

Question 20

What does JSON stand for?

Answer 20

Javascript Object Notation

Question 21

Why is JSON commonly used in web development?

Answer 21

-Transmitting data between a server and a web application.
-Easy for machines to parse and generate JSON data.
-Popular due to its simplicity, readability, and flexibility.

Question 22

What does REST API stand for?

Answer 22

Representational State Transfer Application Programming Interface

Question 23

What does a REST API do?

Answer 23

Play a crucial role in modern web development by enabling diverse applications to communicate and share data over the web in a flexible, efficient, and straightforward manner.

Question 24

Serve JSON on a specific route(create route handler that sends JSON data as the response):

Answer 24

app.get(‘/data’, function(req, res){
const jsonData = {
message: “Hello World”,
numbers: [1, 2, 3, 4, 5]
};
res.json(jsonData);
});

Question 25

What is an .env file?

Answer 25

Configuration file commonly used in Node.js and other server-side applications to manage environment variables

Question 26

In .env, what are enviroment variables?

Answer 26

-Are key-value pairs that define the enviroment in which your application runs.
-Contains sensitive information such API keys, database credentials, or configurations settings.

Question 27

Example of enviroment variables in your .env file:

Answer 27

-PORT=3000
-DATABASE_URL=mongodb://localhost:27017/mydatabase
-API_KEY=your_api_key_here

Question 28

How do you access enviroment variables in your application & show how to access a PORT variable ?

Answer 28

-use the ‘process.env’ object,
-const port = process.env.PORT

Question 29

How do you load the .env file to make the enviroment variables available?

Answer 29

-with a package like ‘dotenv’
-npm install dotenv

Question 30

Once dotenv is installed, what do you add on the top line of your application file?

Answer 30

require(‘dotenv’).config();

Question 31

What is a root-level request logger middleware?

Answer 31

-is middleware that captures and logs incoming HTTP requests at the topmost level of the application’s middleware stack.
-Powerful tool for enhancing the observability, security, and manageability of web applications.
-Gives valuable insights into the application’s usage and behavior, which can aid in debugging, monitoring, and optimizing the application.
-Function that logs information about each incoming request to the server, regardless of the route or endpoint being accessed.

Question 32

Create a middleware function that implements a root-level logger:

Answer 32

app.use((req, res, next) => {
console.log(${new Date().toISOString()} - ${req.method} request to ${req.url});
next(); // Pass control to the next middleware function
});

Question 33

What is the purpose of chaining middleware?

Answer 33

1. Modularization and Reusability: Chaining middleware enables developers to modularize and reuse code for common tasks like authentication, logging, and error handling.
2. Sequential Processing: Middleware functions are executed in a specified order, allowing developers to control the flow of request handling and implement complex logic step by step.
3. Granular Control: Developers can apply different middleware to specific routes or groups of routes, ensuring that each middleware function is applied precisely where needed.
4. Error Handling: Chaining error-handling middleware at the end of the stack centralizes error management and ensures consistent handling of errors across the application.
5. Extensibility and Customization: Middleware chaining offers flexibility to extend or modify application behavior by adding, removing, or reordering middleware functions as needed.

Question 34

Chain middleware to create a time server:

Answer 34

app.get(‘/now’, (req, res, next) => {
req.time = new Date().toString()
next()
}, (req, res) => {
res.json({time: req.time})
});

Question 35

What is a route parameter?

Answer 35

-A route parameter is a dynamic part of a URL path that is used to capture variable values, a piece of data, specified by the client when making a request to the server.
-Route parameters are specified in the route path definition and are denoted by a colon (:) followed by the parameter name.

Question 36

How do you access a route parameter input

Answer 36

with req.params in the route handler function

Question 37

Show an example how a route parameter input looks and how to access them:

Answer 37

app.get(‘/users/:userId’, function(req, res) {
const userId = req.params.userId;

res.send(`User Id: ${userId}`); });

Question 38

What is a query parameter?

Answer 38

-is a component of a URL that is used to provide additional information to a web server when making a request.
-Query parameters are typically appended to the end of a URL following a question mark ? and are structured as key-value pairs separated by an ampersand &.

Question 39

What does a query parameter look like?

Answer 39

http://url/search?q=term&page=2

Question 40

How do you access a query parameter from the client in an express.js application?

Answer 40

through the ‘req.query’ object in the route handler

Question 41

Show an example of one accessing a query parameter from the client:

Answer 41

app.get(‘/search’, (req, res) => {
const qQuery = req.query.q;
const page = req.query.page;

res.send(`Query: ${qQuery}, Page: ${page}`); });

Question 42

What is express.json?

Answer 42

-is a built-in middleware function in Express.js, a popular web application framework for Node.js.
-It is used to parse incoming request bodies with JSON payloads.
-express.json() middleware parses this JSON data and makes it available in the req.body property of the request object.’

Question 43

How can one use express.json in an express.js application?

Answer 43

app.use(express.json());

Question 44

How to access form data thats submitted:

Answer 44

app.post(‘/submit’, function(req, res){
const formData = req.body;

res.json(formData); });

Question 45

What is app.listen()?

Answer 45

its a method that starts a server and listens for incoming requests on a specified port

Question 46

What is app.use()?

Answer 46

-a method that mounts middleware functions at a specified path.
-It is used to configure middleware for handling requests.

Question 47

What are app.get(), app.post(), app.put(), app.delete()?

Answer 47

are methods that define routes for specefic HTTP methods(GET, POST, PUT, DELETE) and specify the handler functions to be executed when the server receives requests for those routes.

Question 48

What is app.all()?

Answer 48

a method similar to the HTTP method-specific routing methods, but it matches all HTTP methods.

Question 49

What is app.route()?

Answer 49

a method that creates a chainable route handler for a specific route.

Question 50

What is app.set()?

Answer 50

a method that sets application settings, which can be retrieved using app.get().

Question 51

What is GET route for the home page? Ex?

Answer 51

-This route serves the home oage of your application.
-Ex.
app.get(‘/’, function(req, res){…});

Question 52

What is GET route for? Ex?

Answer 52

-These routes serve specific resources or data from your express.application.
-Ex.
app.get(/users, function(req, res) {…});

Question 53

What is POST route for submission? Ex?

Answer 53

-This route handles form submissions from the client.
-Ex.
app.post(‘/submit’, function(req, res){…});

Question 54

What is PUT route used for? Ex?

Answer 54

-This route updates existing resources in your application.
-Ex.
app.put(‘users/:id’, function(req, res){…});

Question 55

What is DELETE route used for? Ex?

Answer 55

-This route deletes resources from your application.
-Ex.
app.delete(‘/users/:id’, function(req, res){…});

Question 56

What is Error-handling routes? Ex?

Answer 56

-These routes handle errors that occur during the request-response cycle.
-Ex.
app.use(function(err, req, res, next){…});

Question 57

What are Middleware routes? Ex?

Answer 57

-These routes use middleware functions to perform tasks such as authentication, logging, or data validaton.
-Ex.
app.use(function(req, res, next){…});

Question 58

What is Helmet? How do you use it?

Answer 58

-is a middleware for securing express apps by settings various HTP headers to protect against common vulerabilites, such as XSS (Cross-Site Scripting), Clickjacking, and others.
-Ex.
const helmet = require(‘helmet’);
app.use(helmet());

Question 59

What is Compression? How do you use it?

Answer 59

-is a middleware used to compress HTTP responses, reducing the size of data sent over the network and improving the performance of web applications.
-Ex.
const compression = require(‘compression’);
app.use(compression());

Question 60

What is Cookie Parser? How do you use it?

Answer 60

-is a middleware used to parse cookies attached to the client request. It makes cooke data available under ‘req.cookies’.
-Ex.
const cookieParser = require(‘cookie-parser’);
app.use(cookieParser());

Question 61

What is Cors? How do you use it?

Answer 61

is a middleware used to enable Cross-Origin Resource Sharing (CORS) in express applications, allowing controlled access to resources from different domains.

Question 62

What is Passport.js? How do you use it?

Answer 62

-is primarily known as an authentication library
-it also provides middleware functions that can be used in an Express application’s middleware stack to handle authentication-related tasks, making it a middleware in the context of Express.
Ex.
const passport = require(‘passport’);

// Set up Passport middleware for authentication
app.use(passport.initialize());
app.use(passport.session()); // If using session-based authentication

Question 63

What is Express-validator? How do you use it?

Answer 63

-is specifically designed as middleware for request validation in Express applications.
-It intercepts incoming requests, validates them according to defined rules, and can sanitize the data before passing it along to the route handlers.
Ex.
const { body, validationResult } = require(‘express-validator’);

// Middleware for validating request body using Express-validator
app.post(‘/user’, [
body(‘username’).isEmail(),
body(‘password’).isLength({ min: 5 }),
], (req, res) => {
// Handle request and access validation results using validationResult
const errors = validationResult(req);
if (!errors.isEmpty()) {
return res.status(400).json({ errors: errors.array() });
}
// Proceed with handling the valid request
});

Question 64

What is Connect-flash? How do you use it?

Answer 64

-is middleware used for managing temporary messages in Express applications.
-It allows for storing and displaying flash messages to users between requests, making it part of the middleware stack in an Express app.
Ex.
const flash = require(‘connect-flash’);

// Set up session middleware
app.use(session({
secret: ‘secret’,
resave: false,
saveUninitialized: true
}));
// Initialize and use Connect-flash for flash messages
app.use(flash());