JavaScript

Question 1

What is the purpose of variables?

Answer 1

Purpose of variables is to store data/information.

Question 2

How do you declare a variable?

Answer 2

Declaring a variable you need the variable keyword: var and giving it a name: variable name.

Question 3

How do you initialize (assign a value to) a variable?

Answer 3

You assign a value by using the assignment operator: ‘=‘

Question 4

What characters are allowed in variable names?

Answer 4

Characters allowed in the variable names are letters, dollar sign, and underscore

Question 5

What does it mean to say that variable names are “case sensitive”?

Answer 5

When variables are “case sensitive” the same named variable is different when one of the words are capitalized.

Question 6

What is the purpose of a string?

Answer 6

Purpose of a string is to add new content into a page.

Question 7

What is the purpose of a number?

Answer 7

Purpose of a number is calculating, determining the size of the screen, moving the position of an element, or setting the amount of time an element should take to fade in.

Question 8

What is the purpose of a boolean?

Answer 8

Purpose of a boolean is to determine which part of a script should run.

Question 9

What does the = operator mean in JavaScript?

Answer 9

“=“ means the value is being assigned to a variable

Question 10

How do you update the value of a variable?

Answer 10

You use the same variable and assign it to the new value

Question 11

What is the difference between null and undefined?

Answer 11

undefined is a variable that hasn’t been defined to anything and null is a variable that is intentionally missing a value.

Question 12

Why is it a good habit to include “labels” when you log values to the browser console?

Answer 12

Labels can help us with what we’re referring to specific variables/values.

Question 13

Give five examples of JavaScript primitives.

Answer 13

5 primitives: null, undefined, string, boolean, number

Question 14

What data type is returned by an arithmetic operation?

Answer 14

Number

Question 15

What is string concatenation?

Answer 15

When you’re joining multiple strings into 1 string

Question 16

What purpose(s) does the + plus operator serve in JavaScript?

Answer 16

Adding values and concatenation strings

Question 17

What data type is returned by comparing two values (<, >, ===, etc)?

Answer 17

Boolean

Question 18

What does the += “plus-equals” operator do?

Answer 18

It adds the value to a variable and then assigns the result to the variable

Question 19

What are objects used for?

Answer 19

Objects are used to store/group data

Question 20

What are object properties?

Answer 20

Object properties are variables associated with the object

Question 21

Describe object literal notation.

Answer 21

Object Literal Notation consists of the variable object with properties and methods, and in the properties consists of keys and values, methods consists of functions.

Question 22

How do you remove a property from an object?

Answer 22

delete

Question 23

What are the two ways to get or update the value of a property?

Answer 23

dot or bracket notations

Question 24

What is a function in JavaScript?

Answer 24

Its a set a statements that perform a task

Question 25

Describe the parts of a function definition.

Answer 25

function keyword, name of the function, parameter, and curly braces

Question 26

Describe the parts of a function call.

Answer 26

function name and parenthesis

Question 27

When comparing them side-by-side, what are the differences between a function call and a function definition?

Answer 27

definition uses parameters and has a function code block call uses arguments to pass in

Question 28

What is the difference between a parameter and an argument?

Answer 28

Parameters stores variables that can be used later and is used in a function definition argument is used in a function call

Question 29

Why are function parameters useful?

Answer 29

You pass in different arguments in the parameters

Question 30

What two effects does a return statement have on the behavior of a function?

Answer 30

It stops the code from running it will returns any value in the code block

Question 31

Why do we log things to the console?

Answer 31

It tells us what the code is doing

Question 32

What is a method?

Answer 32

Method is a property of an object that has a function definition

Question 33

How is a method different from any other function?

Answer 33

Methods are assigned with an object property, while a function is not

Question 34

How do you remove the last element from an array?

Answer 34

pop() method

Question 35

How do you round a number down to the nearest integer?

Answer 35

floor() method

Question 36

How do you generate a random number?

Answer 36

random() method

Question 37

How do you delete an element from an array?

Answer 37

shift() method, pop() method, or splice() method

Question 38

How do you append an element to an array?

Answer 38

push() method, or unshift() method

Question 39

How do you break a string up into an array?

Answer 39

split() method

Question 40

Do string methods change the original string? How would you check if you weren't sure?

Answer 40

Does not change. console.log() to check

Question 41

Roughly how many string methods are there according to the MDN Web docs?

Answer 41

Roughly 50 string methods

Question 42

Is the return value of a function or method useful in every situation?

Answer 42

No

Question 43

Roughly how many array methods are there according to the MDN Web docs?

Answer 43

Roughly 40 array methods

Question 44

What three-letter acronym should you always include in your Google search about a JavaScript method or CSS property?

Answer 44

MDN

Question 45

Give 6 examples of comparison operators.

Answer 45

6 comparison operator: equal (=), not equal (!=), strictly equal (===), strictly not equal (!===), greater than (>), greater than or equal (>=), less than (<), less than or equal (<=).

Question 46

What data type do comparison expressions evaluate to?

Answer 46

Boolean

Question 47

What is the purpose of an if statement?

Answer 47

It is to run the code if the condition is met

Question 48

Is else required in order to use an if statement?

Answer 48

No

Question 49

Describe the syntax (structure) of an if statement.

Answer 49

if (condition) { statement } else { statement }

Question 50

What are the three logical operators?

Answer 50

logical AND (&&), logical OR (| |), logical NOT (!)

Question 51

How do you compare two different expressions in the same condition?

Answer 51

Compare two expressions with the logical operator

Question 52

What is the purpose of a loop?

Answer 52

Its to repeat a task a set number of times.

Question 53

What is the purpose of a condition expression in a loop?

Answer 53

To cause a loop to end.

Question 54

What does "iteration" mean in the context of loops?

Answer 54

It is when the condition passes in the loop.

Question 55

When does the condition expression of a while loop get evaluated?

Answer 55

Before executing the statement

Question 56

When does the initialization expression of a for loop get evaluated?

Answer 56

The beginning of the loop

Question 57

When does the condition expression of a for loop get evaluated?

Answer 57

Before each loop iteration

Question 58

When does the final expression of a for loop get evaluated?

Answer 58

At the end of each loop interation

Question 59

Besides a return statement, which exits its entire function block, which keyword exits a loop before its condition expression evaluates to false?

Answer 59

When the condition expression evaluates to false

Question 60

What does the ++ increment operator do?

Answer 60

It adds one to variable in the initial conditional expression

Question 61

How do you iterate through the keys of an object?

Answer 61

for ... in loop

Question 62

Why do we log things to the console?

Answer 62

It tells us what the code is doing

Question 63

What is a "model"?

Answer 63

The model is the DOM tree made up of objects. Any representation of the DOM.

Question 64

Which "document" is being referred to in the phrase Document Object Model?

Answer 64

The document is the webpage; it can be displayed in the browser or the HTML source.

Question 65

What is the word "object" referring to in the phrase Document Object Model?

Answer 65

“object” refers to the object of the document.

Question 66

What is a DOM Tree?

Answer 66

DOM Tree is a model of a web page.

Question 67

Give two examples of document methods that retrieve a single element from the DOM.

Answer 67

To get individual nodes, you use getElementById() or querySelector.

Question 68

Give one example of a document method that retrieves multiple elements from the DOM at once.

Answer 68

To get multiple elements at once, you use getElementByClassName() - returns an HTML collection, getElementsByTagName(), or querySelectorAll() - returns a static NodeList.

Question 69

Why might you want to assign the return value of a DOM query to a variable?

Answer 69

Because you might work with an element more than once.

Question 70

What console method allows you to inspect the properties of a DOM element object?

Answer 70

console.dir()

Question 71

Why would a