Express.js Routing and Request Handling

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Questions and Answers

What command is used to install Pug as a templating engine in Express?

npm install pug

npm add pug

npm install pug --save

npm install --save pug (correct)

When setting the view engine for an Express application to Pug, which command is used?

app.set('view engine', 'pug') (correct)

app.add('view engine', 'pug')

app.configure('view engine', 'pug')

app.use('view engine', 'pug')

What does the `res.send()` function do in an Express application?

It defines middleware for the application.

It sends an HTTP request to a specified URL.

It sends a response back to the requesting client. (correct)

It handles routing for different HTTP methods.

Which function is correctly used to define a route that handles GET requests in an Express app?

app.get('/path', handler) Signup and view all the answers

How are nested tags represented in Pug?

By indentation Signup and view all the answers

What is the primary purpose of middleware in Express applications?

To process requests before they reach the route handler. Signup and view all the answers

What is the purpose of the pipe operator (|) in Pug?

To insert multiline text Signup and view all the answers

Which of these file extensions are typically used for Pug template files?

.pug Signup and view all the answers

If a POST request is made to the `/hello` route, what will the response be?

You just called the post method at '/hello'! Signup and view all the answers

What is the correct way to reference a module located in the same folder as the Node.js file?

require('./myfirstmodule') Signup and view all the answers

What does the method `app.all()` do in an Express application?

Defines a single route for all HTTP methods. Signup and view all the answers

What is a common way to test a POST request in an Express app using the terminal?

curl -X POST <a href="http://localhost:3000/hello">http://localhost:3000/hello</a> Signup and view all the answers

What will be the output when rendering the first_view.pug file?

Hello World! Signup and view all the answers

What function is used to create a server in the provided Node.js example?

http.createServer() Signup and view all the answers

In an Express application, what does the `app.listen(port)` function do?

It initiates the server to listen for connections on a specified port. Signup and view all the answers

What is meant by 'handler' in the context of defining routes in Express?

A callback function that executes upon a matching request. Signup and view all the answers

What validation is performed on the 'year' field in the POST route?

It checks if the year is a four-digit number. Signup and view all the answers

Which HTTP status code is returned when the required fields are missing or invalid?

400 Bad Request Signup and view all the answers

What is the structure of the response when a new movie is created successfully?

An object with a 'message' and the 'location' of the new movie. Signup and view all the answers

How does the route determine the new ID for a movie?

It increments the ID of the last movie in the array. Signup and view all the answers

What command is suggested to test if a new movie was added to the movies object?

curl -X GET <a href="http://localhost:3000/movies/105">http://localhost:3000/movies/105</a> Signup and view all the answers

What is the purpose of the renderFile function in Pug?

To compile a Pug template from a file Signup and view all the answers

Which HTTP method is used to modify an existing resource or create one if it does not exist?

PUT Signup and view all the answers

What does the 'pretty' option in Pug do?

It makes the HTML output more readable Signup and view all the answers

Which statement about the GET method is true?

It should not have any side effects Signup and view all the answers

What is indicated by the output of the 'res' variable in the Pug example?

It displays the rendered HTML output Signup and view all the answers

What occurs when the DELETE method is invoked with a specified resource?

The resource is removed from the server Signup and view all the answers

When merging locals and options using Object.assign, which of the following pairs are being combined?

Template variables and rendering options Signup and view all the answers

In RESTful APIs, what is the role of the URIs?

To uniquely identify resources for manipulation Signup and view all the answers

What is the purpose of the `render` function in Pug?

To convert a template string and context data into the final output. Signup and view all the answers

How are comments created in Pug?

Using // followed by the comment. Signup and view all the answers

What does the code `div.container.column.main#division(width = '100', height = '100')` represent?

An HTML tag with attributes, classes, and an ID. Signup and view all the answers

What will be the output of the following code when executed? `console.log(output);` in example.js.

John Doe is a gardener Signup and view all the answers

What does the `compileFile` function do in Pug?

It compiles a Pug template to a function for multiple renders. Signup and view all the answers

In the context of Pug, what is represented by `#{name}` in a template string?

A variable that gets replaced by its value. Signup and view all the answers

In the example provided, which statement about the output of `cfn({'name': 'Roger Roe'});` is correct?

It outputs 'Hello Roger Roe!' Signup and view all the answers

Which of the following describes the use of the syntax for attributes in Pug?

Attributes are defined in parentheses as a comma-separated list. Signup and view all the answers

Study Notes

Request and Response Objects

The req object represents the HTTP request and contains properties for the request query string, parameters, body, HTTP headers, etc.
The res object represents the HTTP response that the Express app sends when it receives an HTTP request.
The res.send() function takes an object as input and sends it to the requesting client.

Routing in Express

Web frameworks provide resources such as HTML pages, scripts, images, etc. at different routes.
Routes are defined using the app.method(path, handler) function,
METHOD can be any HTTP verb like get, set, put, or delete. It defines what type of request the route should handle.
path is the route at which the request will run.
handler is a callback function that executes when a matching request type is found on the relevant route.
The app.all(path, handler) method can handle all types of HTTP methods at a particular route using the same function.

Middleware

Middleware is a function that has access to the request and response objects, and the next middleware in the stack.
It can be used to perform tasks such as logging, authentication, and authorization.
It is generally used for defining middleware, which we'll discuss in the middleware.

Templating with Pug

To use Pug with Express, install it with npm install --save pug.
Set the view engine to pug using app.set('view engine', 'pug') and the views directory using app.set('views','./views').
Pug simplifies HTML markup, removes the need for closing tags, and provides a cleaner syntax for defining classes and IDs using . and #.
Pug enables a more efficient way of writing code.
Pug is capable of doing more than simplifying HTML markup.

Pug Features

Simple Tags: Tags are nested according to their indentation. Pug provides mechanisms to write them using the indentation, removing the need for explicit closing tags.
Comments: Pug uses the same syntax as JavaScript (//) for creating comments, which are converted to HTML comments ().
Attributes: To define attributes, use a comma-separated list of attributes in parentheses. The attributes can be accessed using the #{} operator in the template.

Rendering Pug Templates

Rendering from String: The render function from the pug module compiles a Pug template string and its data into an HTML string.
compileFile Function: Compiles a Pug template from a file to a function, which can be rendered multiple times with different locals.
renderFile Function: Compiles a Pug template from a file and renders it with locals to an HTML string.

HTTP Methods

GET: Requests a representation of the specified resource. Should only retrieve data and have no other side effects.
POST: Requests the server to accept the data enclosed in the request as a new object/entity of the resource identified by the URI.
PUT: Requests the server to accept the data enclosed in the request as a modification to an existing object identified by the URI. If it doesn't exist, it should create one.
DELETE: Requests the server to delete the specified resource.

RESTful APIs

RESTful APIs use URIs and HTTP methods to represent resources and operations on them.
The table below summarizes how HTTP verbs should be used and how URIs should be named:

HTTP Method	Action	URI
GET	Retrieve a list of resources	`/movies`
GET	Retrieve a single resource	`/movies/:id`
POST	Create a new resource	`/movies`
PUT	Update an existing resource	`/movies/:id`
DELETE	Delete a resource	`/movies/:id`

Creating a Movies API

You can create a RESTful interface to create a new movie resource using a route defined with the router.post() method in the Express.
You can test the route by using the curl command with the -X POST option, providing the data as a query string in the URL.
To update an existing resource, you can use the PUT method with the id of the resource in the URI.
To delete a resource, you can use the DELETE method with the id of the resource in the URI.

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Description

This quiz focuses on the foundational concepts of routing and request-response handling in Express.js. It covers the roles of the req and res objects, the definition of routes, and the use of middleware. Test your knowledge on how these components work together in a Node.js web application.