Node.js

Question 1

What is Node.js?

Answer 1

Node.js is a program that allows JavaScript to be run outside of a web browser.

Question 2

What can Node.js be used for?

Answer 2

It is commonly used to build back ends for Web applications, command-line programs, or any kind of automation that developers wish to perform.

Question 3

What is a REPL?

Answer 3

A read–eval–print loop (REPL), also termed an interactive toplevel or language shell, is a simple interactive computer programming environment that takes single user inputs, executes them, and returns the result to the user; a program written in a REPL environment is executed piecewise.

Question 4

When was Node.js created?

Answer 4

May 27, 2009

Question 5

What is the process object in a Node.js program?

Answer 5

Is a global variable that provides information about, and control over, the current Node.js process.

The process object is an instance of EventEmitter.

Question 6

How do you access the process object in a Node.js program?

Answer 6

Call it as you would any other object in JS, it’s global

Question 7

What is the data type of process.argv in Node.js?

Answer 7

array or strings

Question 8

What does proces.argv do?

Answer 8

The process.argv property returns an array containing the command line arguments passed when the Node.js process was launched.

$ node process-args.js one two=three four

0: /usr/local/bin/node
1: /Users/mjr/work/node/process-args.js
2: one
3: two=three
4: four

Question 9

What is a JavaScript module?

Answer 9

each separate js file

Question 10

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

Answer 10

(function(exports, require, module, __filename, __dirname) {
// Module code actually lives in here
});

Question 11

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

Answer 11

console
process

Question 12

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

Answer 12

Makes things available to other modules in your node. js program

Question 13

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

Answer 13

call the require function, pass in a relative path, and assign its return value to a variable

Question 14

What is the JavaScript Event Loop?

Answer 14

The event loop looks at the stack and the task queue. I the stack is empty, it pushed it from the task queue to the stack, which effectively runs it.

Question 15

What is different between “blocking” and “non-blocking” with respect to how code is executed?

Answer 15

blocking code is occupying the call stack.

Question 16

What is a directory?

Answer 16

A file that lists other files and directories.

Question 17

What is a relative file path?

Answer 17

a path to a file from where you are currently

Question 18

What is an absolute file path?

Answer 18

starts from the root of the file system (starts with a slash)

Question 19

What module does Node.js include for manipulating the file system?

Answer 19

fs

Question 20

What method is available in the Node.js fs module for writing data to a file?

Answer 20

fs.writeFile

Question 21

Are file operations using the fs module synchronous or asynchronous?

Answer 21

asynchronous

Question 22

What is NPM?

Answer 22

Node packaging manager
npm is the world’s largest software registry. A way for you to reuse code from other developers and for you to share code with them

npm consists of three distinct components:
the website
the Command Line Interface (CLI)
the registry (database of info about packages that people are sharing)

Question 23

What is a package?

Answer 23

Bits of reusable code (also sometimes called modules). A package is a directory with one of more files in it that also has a file called package.json with some metadata about this package.

Question 24

How can you create a package.json with npm?

Answer 24

1. On the command line, navigate to the root directory of your package.

cd /path-to-package

2. Run the following command:

npm init –yes

Question 25

What is a dependency and how to you add one to a package?

Answer 25

packages that another package depends on. Packages required by your application in production.

You can add dependencies to a package.json file from the command line or by manually editing the package.json file.
npm install

Question 26

What happens when you add a dependency to a package with npm?

Answer 26

When you (or another user) run npm install, npm will download dependencies and devDependencies that are listed in package.json that meet the semantic version requirements listed for each

installs the dependencies into the node_modules folder

updates package json to list that package dependency

Question 27

How do you add express to your package dependencies?

Answer 27

npm install express

Question 28

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

Answer 28

the listen method

Question 29

How do you mount a middleware with an Express application?

Answer 29

the use method

Question 30

What are controlled components?

Answer 30

The value is kept in a component state.
Listen for when that value changes and update that state

Question 31

What two props must you pass to an input for it to be “controlled”?

Answer 31

value prop to tell the input what it’s current value is
onChange

Question 31

What two props must you pass to an input for it to be “controlled”?

Answer 31

value prop to tell the input what it’s current value is
onChange

Question 32

What does express.static() return?

Answer 32

a function
static files

Question 33

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

Answer 33

The directory name of the current module.
it’s an absolute path

Question 34

What does the join() method of Node’s path module do?

Answer 34

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