Introduction

Question 1

What is NodeJS?

Answer 1

Node is a JS run time that allows you to run code on the server.

Question 2

What engine does Node use?

Answer 2

Node uses the V8 engine and adds JS features.

Question 3

In Node how would you work the file system?

Answer 3

In Node.js, you work with the file system by importing the fs (file system) module. This module provides an object with methods that allow you to interact with the file system.

Question 4

How do you import modules in Node?

Answer 4

You import modules by using the require keyword.

Question 5

What is the purpose of JavaScript in the backend, and why do we use it in the backend?

Answer 5

We use JavaScript for databases, authentication, input validation, business logic, and more. This is done to ensure that clients cannot view or manipulate the server-side code.

Question 6

How do clients access our code since it’s in the backend?

Answer 6

Although they can not directly access it, they can communicate with it using the request and response pattern.

Question 7

What are other purposes you can use Node for?

Answer 7

You can use it for more than just server-side code. You can use it for utility scripts, build tools, etc.

Question 8

What is Node’s role in web development?

Answer 8

We use it to create a server and listen to incoming requests. Additionally, we use it to handle business logic, such as handling requests, validating input, connecting to databases, etc. Finally, we handle the responses, such as returning JSON or HTML.

Question 9

What are the core modules in Node

Answer 9

HTTP, HTTPS, FS, PATH, AND OS

Question 10

Using the HTTP module, how would you create a server, listen for requests, and send responses? Try to create a server yourself.

Answer 10

Create a server you call the createServer method. This method takes in a function. This function takes in two arguments, a response and a request. this function will run every time a request reaches our server.
This createServer method returns a server. We store this server into a variable in then we can call methods on this server. One of these methods is the listen. This method will keep our script running to listen for any incoming requests. This method takes in two arguments, the port and the host name.

Question 11

Why is the event loop important in Node?

Answer 11

Node.js depends on the event loop. This is because the event loop will keep running as long as there are event listeners triggered. One of those event listeners is the callback function in the createServer method. This function is an ongoing event listener.

Question 12

When using the request object, what are the important methods and properties?

Answer 12

The most important properties and methods are URL, METHOD, and HEADERS. The URL property indicates the requested URL. The method property specifies the HTTP method used (e.g., GET, POST). The headers property provides details about the request headers, such as the host, connection, and accepted content types.

Question 13

How can we send data back in Node?

Answer 13

In Node.js, we can send data back by using the response object. First, we call the setHeader method on the response object to specify the content type we want to send back. For example, we might send HTML. After setting the content type, we can use the write method on the response object to send the HTML content. Finally, we call the end method to complete the response.

Question 14

How do we change the status code and what is the status code for redirecting?

Answer 14

The code for redirecting: res.statusCode = 302;

Question 15

How can we redirect someone in Node?

Answer 15

res.setHeader(“Location”, “/”);

Question 16

What method is used to listen for events on a request object?

Answer 16

In Node.js, req.on is used to listen for events on a request object (req). When you use req.on(‘data’, callback), you’re saying, “Hey, whenever there’s incoming data on this request, run this callback function.” It’s commonly used for handling data streams, like when uploading files or processing large amounts of data from a client.

Question 17

When we have received all the data in the “data” callback function, what can we do?

Answer 17

You use req.on(‘end’, callback), you’re saying, “Hey, when the incoming data is all received, run this callback function.” It signals that the entire request body has been received, and you can now process or handle that data in the callback function. It’s commonly used to finalize processing after receiving all the chunks of data.

Question 18

What is a buffer?

Answer 18

In Node.js, a Buffer is like a container for raw binary data.

Question 19

When processing our data in the “data” callback function, what form does the data arrive in?

Answer 19

The data arrives as a buffer.

Question 20

How do we convert our buffers into real data?

Answer 20

Take an array of Buffer objects (body) and join them into a single Buffer. Then, .toString() converts that combined Buffer into a string.

Question 21

What is event-driven code?

Answer 21

In event-driven programming, actions are triggered by events.

Question 22

Why do we use the return statements on certain request methods?

Answer 22

We use return here to ensure that after handling the request, we exit the function and don’t continue executing code further down.

Question 23

In Node, what execution style does it revolve around itself?

Answer 23

The concept of event emitters and listeners.

Question 24

What are the drawbacks of using writeFileSync?

Answer 24

writeFileSync is synchronous, meaning if the operation takes a long time, it will block other code execution. Instead, we should use writeFile. This method accepts three arguments: the file name, the data, and a callback function. The callback function handles errors in case the task fails. Inside this callback function, we specify the code we want to execute once the file is written.

Question 25

What type of events does the event loop handle and what does it not handle?

Answer 25

The event loop handles fast-loading events. It does not handle larger events.

Question 26

What is responsible for large events?

Answer 26

hey are sent to the worker pool. The worker pool is also managed by Node. This worker pool is responsible for all the heavy lifting.

Question 27

Where is the worker pool?

Answer 27

This worker pool is sort of detached from your code because it runs on different threads.

Question 28

What happens once the worker is done loading the bigger content?

Answer 28

Once this worker is done, it will then trigger the callback. So, since the event loop is responsible for the callback functions, it will end up in the event loop.

Question 29

Tell me about the process of the event loop.

Answer 29

1. The event loop starts by checking for any timer callbacks.
2. it checks for any other pending callbacks, which may include blocking and long-blocking operations.
3. After completing these callbacks, it enters the poll phase. In this phase, it retrieves new I/O events and executes their callbacks. Additionally, it may check for any deferred callbacks or jump to the timers phase if necessary.
4. Following the poll phase, the check phase occurs, during which setImmediate callbacks are executed.
5. Finally, the event loop enters the close callbacks phase, where it executes all close event callbacks.

Question 30

How do we create a package.json file in our project?

Answer 30

You can create a package file by typing npm init into the terminal. This will create a package.json file for your project. In this file, you can add scripts, such as a start script. This will allow you to start your applications faster.

Question 31

What are dependencies?

Answer 31

These are third-party packages that are not included with Node.js. These packages enable you to perform various functions, such as parsing data or validating input. Some of these dependencies are meant to be used for development, while others are for production. For example, nodemon is meant to be used in development. The –save flag will install a package as a production dependency, and the –save-dev flag will install a package only for development. There is also -g this will install everywhere in your machine.

Question 32

What is Nodemon?

Answer 32

Nodemon is a dependency that automatically watches for file changes and restarts the application if any are detected. This is convenient because we don’t have to spend time exiting our server whenever there is a change.

Question 33

What are the three types of errors?

Answer 33

Syntax, Runtime, and logical.