LFZ Quiz questions (Senior parts)

Question 1

What is a JavaScript module?

Answer 1

In the Node.js module system, each file is treated as a separate module.
Single JS file.

Question 2

What is a JavaScript module?

Answer 2

Single JS file.
In the Node.js module system, each file is treated as a separate module.

Question 3

What values are passed into a Node.js module’s local scope?

Answer 3

exports, require, module, __filename, and __dirname

Question 4

Give two examples of truly global variables in a Node.js program.

Answer 4

https://nodejs.org/docs/latest-v10.x/api/globals.html

Global Objects

Class: Buffer
\_\_dirname
\_\_filename
clearImmediate(immediateObject)
clearInterval(intervalObject)
clearTimeout(timeoutObject)
console
exports
global
module
process
require()
setImmediate(callback[, ...args])
setInterval(callback, delay[, ...args])
setTimeout(callback, delay[, ...args])
URL
URLSearchParams
WebAssembly

==> module scope: It appears global
\_\_dirname
\_\_filename
exports
module
require()

Question 5

What is the purpose of module.exports in a Node.js module?

Answer 5

Module exports are the instruction that tells Node.js which bits of code (functions, objects, strings, etc.) to “export” from a given file so other files are allowed to access the exported code.

To understand modules in Node.js, I like to imagine all my modules written together in one file (not as modules), and then imagine what code I’d need to make that happen. The code would look like each module wrapped in a function and given an argument, which is the current module.

Question 6

How do you import functionality into a Node.js module from another Node.js module?

Answer 6

Require is a function we can use to import other modules.

Require will search for modules using the following rules:

Is there a core module with the required path? Yes, return it.
Is there a node_modules package with the name of the path? Yes, return it.
Is there a file (or directory!) with the name of the given path? Yes, return it.
Otherwise, throw an error.

Question 7

What are serialization and deserialization and why are they useful?

Answer 7

Serialization is the process of turning an object in memory into a stream of bytes so you can do stuff like store it on disk or send it over the network.

Deserialization is the reverse process: turning a stream of bytes into an object in memory.

Question 8

What is a server?

What is a client?

Answer 8

Client–server model is a distributed application structure that partitions tasks or workloads between the providers of a resource or service, called servers, and service requesters, called clients.
Servers are classified by the services they provide. For example, a web server serves web pages and a file server serves computer files

Question 9

Which HTTP method does a browser issue to a web server when you visit a URL?

Answer 9

GET

Question 10

What is the format of an HTTP request message?

Answer 10

• Start line: HTTP method, request target, HTTP version
• Headers: General headers, Response headers, Entity headers
• Body: Single-resource bodies(Content-Type and Content-Length), Multiple-resource bodies(HTML Forms)

Question 11

What is the format of an HTTP response message?

Answer 11

• Status line: protocol version, status code, status text
• Headers: General headers, Response headers, Entity headers
• Body: responses with a status code that sufficiently answers the request without the need for corresponding payload

Question 12

How do you add express to your package dependencies?

Answer 12

npm install express

Question 13

What Express application method binds the server to a network PORT?

Answer 13

app.listen([port[, host[, backlog]]][, callback])
Binds and listens for connections on the specified host and port. This method is identical to Node’s http.Server.listen().

Question 14

How do you register a middleware with an Express application?

Answer 14

We can use use method.

ex) app.use

Question 15

Which objects does an Express application pass to your middleware to manage the request/response lifecycle of the server?

Answer 15

request and response objects

Question 16

(express-sendfile)

What is the Content-Type header of HTTP requests and responses used for?

Answer 16

Content-Type response HTTP header field based on the filename’s extension.
ex)
Content-Type: application/javascript; charset=UTF-8
Content-Type: text/css; charset=UTF-8
Content-Type: text/html; charset=UTF-8

Question 17

(express-static)

What does express.static() return?

Answer 17

Create a new middleware function to serve files from within a given root directory. The file to serve will be determined by combining req.url with the provided root directory. When a file is not found, instead of sending a 404 response, this module will instead call next() to move on to the next middleware, allowing for stacking and fall-backs.

Question 18

(express-static)

What is the local __dirname variable in a Node.js module?

Answer 18

The directory name of the current module

Question 19

(express-static)
What does the join() method of Node's path module do?

Answer 19

The path.join() method joins all given path segments together using the platform-specific separator as a delimiter, then normalizes the resulting path.

Question 20

(express-get-json)

What is the appropriate Content-Type header for requests and responses that contain JSON in their bodies?

Answer 20

Content-Type: application/json; charset=utf-8

Question 21

(express-post-json)

What does the express.json() middleware do and when would you need it?

Answer 21

It parses incoming requests with JSON payloads and is based on body-parser.
If servers need to handle JSON file type, express.json() middleware must be called before using it.

Question 22

(express-delete)

What is the significance of an HTTP request’s method?

Answer 22

A route path and request URL can be determined by requesting methods.

Question 23

(webpack-intro)

What is Webpack?

Answer 23

t’s a tool that lets you bundle your JavaScript applications (supporting both ESM and CommonJS), and it can be extended to support many different assets such as images, fonts and stylesheets. Webpack applies the concept of modules to any file in your project.

Question 24

(webpack-intro)

How do you add a devDependency to a package?

Answer 24

npm install –save-dev
or
npm install -D

Question 25

(webpack-intro)

What is an NPM script?

Answer 25

npm run build

npm command line

Question 26

(webpack-intro)

How do you execute Webpack with npm run?

Answer 26

“scripts”: {
“build”: “webpack”,
}

ex)
"scripts": {
    "dev": "webpack --mode=development --watch --devtool=source-map",
    "build": "webpack --mode=preduction"
}

Question 27

(es-modules)
What is an ES6 module and how is it different from a CommonJS module?

Answer 27

ES6 module can support browsers whereas CommonJS supports only server sides. ES6 module supports AMD(Asynchronous Module Definition)