ES6

Question 1

What is a code block? What are some examples of a code block?

Answer 1

Code within {}. Examples include - functions, loops, conditionals. For loop (let i = 0; i < length; i++) is part of the following block.

Question 2

What does block scope mean?

Answer 2

It means that a variable is not attached to the global window object and is only referenced inside the current code block.
What happens inside the code block, stays inside the code block.

Question 3

What is the scope of a variable declared with const or let?

Answer 3

IT IS BLOCK SCOPE. It depends where it is declared, either inside a code block making it block scoped or outside. Allows using the same variable name with the let keyword outside a code block and reusing it with a second let keyword inside a code block.

Question 4

What is the difference between let and const?

Answer 4

The difference is that let can be reassigned but const cannot be reassigned.

Question 5

Why is it possible to .push() a new value into a const variable that points to an Array?

Answer 5

.push is not reassignment of a new array, only changing/mutating the original array.

Question 6

How should you decide on which type of declaration to use?

Answer 6

Start with const, till the linter/compiler gets mad. Const should be used if no reassignment is needed. Let should be used if the variable will change throughout the code file.

Question 7

What is the syntax for writing a template literal?

Answer 7

Backticks with ${} to denote substitutions.

Question 8

What is “string interpolation”?

Answer 8

Concatenating strings and string substitutions.

Question 9

What is destructuring, conceptually?

Answer 9

Pulling individual values from objects and arrays and assigning them to a variable.

Question 10

What is the syntax for Object destructuring?

Answer 10

const { property: variableName } = original object
don’t need variable name if using property name for the variable name.

Question 11

What is the syntax for Array destructuring?

Answer 11

Using brackets with the variables in the position of the array you want, assigned to the array.
const [a, , b] = array

Question 12

How can you tell the difference between destructuring and creating Object/Array literals?

Answer 12

The side of the equal sign which the curly braces or brackets come on.

Question 13

What is the syntax for defining an arrow function?

Answer 13

params or () => single line implied return declaration.
params or () => { code }

Question 14

When an arrow function’s body is left without curly braces, what changes in its functionality?

Answer 14

It implies a return statement of one expression only.

Question 15

What is a CLI?

Answer 15

Command line interface - usually called the console or terminal

Question 16

What is a GUI?

Answer 16

A graphical user interface, most common for users, VS code is a GUI for coders, that also contains a CLI.

Question 17

Give at least one use case for each of the commands listed in this exercise.
man
cat
ls
pwd
echo
touch
mkdir
mv
rm
cp
history

Answer 17

man -open a manual of a cmd
cat - print contents of a file
ls - ls files and directories
pwd - prints the current or working directory
echo - logs a string
touch - move a file - change timestamp
mkdir - make a new directory
mv - rename files or move
rm - remove files
cp - copy files
history - prints cmd line history

Question 18

What are the three virtues of a great programmer?

Answer 18

hubris, impatience, laziness

Question 19

What are the 3 components of a fullstack Web architecture?

Answer 19

frontend(presentation), backend server(logic handling), database

Question 20

What is Node.js?

Answer 20

Allows JavaScript to be run outside of a browser.

Question 21

What can Node.js be used for?

Answer 21

to build servers and other automation in command line programs.

Question 22

What is a REPL?

Answer 22

A Read-eval-print loop. The part that allows you to run JavaScript code, like our developer tools in our browser.

Question 23

When was Node.js created?

Answer 23

2009. may 27

Question 24

What backend languages have you heard of?

Answer 24

express, Node, PHP, RUBY, C++, Java, C#

Question 25

What is a computer process?

Answer 25

executable task

Question 26

Roughly how many computer processes are running on your host operating system (Task Manager or Activity Monitor)?

Answer 26

290

Question 27

Why should a full stack Web developer know that computer processes exist?

Answer 27

Processes run our code.

Question 28

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

Answer 28

It is a global object, like the window object in developers tools and contains many properties and methods and event listeners.

Question 29

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

Answer 29

As process? or process.property

Question 30

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

Answer 30

process.argv is an array of strings with the first 2 index representing the directory/file locations?

Question 31

How do you access the command line arguments in a Node.js program?

Answer 31

You can access the indexes of the process.argv of index 2+ depending on your arguments.
I.E.
node file.name argument1 argumentN
Will pass those arguments into the js file and can be retrieved with process.argv[2] and process.argv[3]. Potentially going to pass the return of another file as arguments to another file? Would have to be json.

Question 32

What is a JavaScript module?

Answer 32

A JavaScript file.

Question 33

What are the advantages of modular programming?

Answer 33

You can separate functionality and keep code cleaner and easier to read.

Question 34

In JavaScript, how do you make a function in a module available to other modules?

Answer 34

Export functions with the export keyword, only one can be export default.

Question 35

In JavaScript, how do you use a function from another module?

Answer 35

You can import functions with the import keyword.

Question 36

What is the JavaScript Event Loop?

Answer 36

It’s a place where code goes to wait to be called back onto the ‘stack’ when the stack is empty.

Question 37

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

Answer 37

Blocking stops other code from running(single-threaded), where in non-blocking code is put onto a que when it can run.

Question 38

What does Array.filter do?

Answer 38

Creates a new array from an array based on a condition.

Question 39

What should the callback function return?

Answer 39

Boolean, whether or not to keep the array.

Question 40

What is Array.filter useful for?

Answer 40

Removing unwanted values from an array.

Question 41

What does Array.map do?

Answer 41

Manipulates every element in an array and returns it as a new array.

Question 42

What should the callback function return?

Answer 42

Return, a value of the manipulated element.

Question 43

What is Array.map useful for?

Answer 43

Doing one thing to all elements of an array. Remember for React.

Question 44

What does Array.reduce do?

Answer 44

Combines all the elements of an array, in a particular way to a single value.

Question 45

What action should the callback function perform?

Answer 45

Perform an expression on the current value to combine with the accumulated value.

Question 46

What should the callback function return?

Answer 46

Should return the accumulated value.

Question 47

What is Array.reduce useful for?

Answer 47

Turning an array into one value.

Question 48

What is a directory?

Answer 48

A file folder.

Question 49

What is a relative file path?

Answer 49

The location of a file based on another file.

Question 50

What is an absolute file path?

Answer 50

The full path location of a file based on the root. /<– starts a absolute

Question 51

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

Answer 51

node fs, which is node File System.

Question 52

What method is available in the node:fs module for reading data from a file?

Answer 52

fs.readfile

Question 53

What method is available in the node:fs module for writing data to a file?

Answer 53

The writefile method of the fs object.

Question 54

Are file operations using the fs module synchronous or asynchronous?

Answer 54

They are asynchronus. The promise one is better.

Question 55

What are JavaScript classes?

Answer 55

They define a particular group of objects. Template.

Question 56

When would you want to use a class?

Answer 56

When you have multiple objects with similar properties and methods.

Question 57

When would you want to use a class?

Answer 57

When you have multiple objects with similar properties and methods.

Question 58

How do you declare a class?

Answer 58

With the class keyword followed by the class’s name. A constructor code block.

Question 59

How do you inherit from another class?

Answer 59

Using the extends keyword. And calling super() in the constructor.

Question 60

Why would you want to inherit from another class?

Answer 60

Your object shares the same properties and methods of this class plus more.

Question 61

How do you add methods and properties to a class?

Answer 61

You add properties in it’s constructor body and then declare methods after.

Question 62

What does fetch() return?

Answer 62

A promise which will be a response object.

Question 63

What is the default request method used by fetch()?

Answer 63

GET

Question 64

How do you specify the request method (GET, POST, etc.) when calling fetch?

Answer 64

pass a request object to the options argument.

Question 65

How does fetch report errors?