JavaScript Quiz Questions

Question 1

What is a variable?

Answer 1

A container for storing data

Question 2

Why are variables useful?

Answer 2

You can reuse them, assign value to them, use for dynamic operations

Question 3

What two special characters can a variable begin with?

Answer 3

A $sign or _underscore

Question 4

How do you declare a variable?

Answer 4

The ‘var’ keyword

Question 5

How do you assign a value to a variable?

Answer 5

with the equals sign

Question 6

Are variables case sensitive?

Answer 6

Yes

Question 7

Which words cannot be used as variable names?

Answer 7

other keywords in JS

Question 8

What is a string?

Answer 8

A series of characters stored within a pair of “” marks

Question 9

What is the string concatenation operator?

Answer 9

+ sign

Question 10

What is the difference when it comes to using single quotes or double quotes ( ‘ ‘ or “ “ )?

Answer 10

No difference, but you can use apostrophes in “ “ double quotes.

Question 11

How do you escape quotation characters?

Answer 11

With a backslash

Question 12

What is type coercion?

Answer 12

The process of converting one data type value to another

Question 13

What is a number in JavaScript?

Answer 13

a primitive datatype

Question 14

What is an arithmetic operator?

Answer 14

operators that do math

Question 15

Name four of the arithmetic operators?

Answer 15

+, -, *, /, %

Question 16

What is the order of execution?

Answer 16

PEMDAS

Question 17

What is a boolean?

Answer 17

A datatype with the values of true or false

Question 18

What is a comparison operator?

Answer 18

Compares two values and returns a true or false value

Question 19

What is the difference between undefined and null?

Answer 19

Undefined is a variable that has been declared but no value has been assigned.
Null must be assigned and is an empty value.

Question 20

What advantages do you see with using a grid system?

Answer 20

Eliminates a lot of repetition, can be saved for later use,

More organized, and segmented.

Question 21

Why are media queries crucial to responsive grid designs?

Answer 21

Allows for the page to be viewed on various device sizes so that nothing is cut out or removed due to sizing changes.

Question 22

What is a function?

Answer 22

A list of actions to be performed

Question 23

Why are functions useful?

Answer 23

Can be reused for multiple purposes, so they save a lot of time

Question 24

How do you call a function?

Answer 24

name of the function with () parenthesis

Question 25

What are the parts of a function definition?

Answer 25

``` function keyword, function definition (name) (parameters) {code} ```

Question 26

What is the difference between a parameter and an argument?

Answer 26

Parameters are declared when the function is created | Arguments are the data you pass into the function

Question 27

Why is it important to understand truthy and falsy values?

Answer 27

Can be important when using them in conditional statements or in comparisons, in case type coercion is used.

Question 28

Why is the typeof null an object?

Answer 28

it is a bug

Question 29

What is the difference between null and undefined?

Answer 29

Undefined is a declared variable that has not been assigned a value. Null is an assigned empty value. Undefined is a type, null is an object

Question 30

Why do you always use === for comparisons?

Answer 30

because of type coercion, you might get an inaccurate result

Question 31

Why do you want to avoid using == for comparison?

Answer 31

because of type coercion, you might get an inaccurate result

Question 32

Do all if statements require an else statement?

Answer 32

No

Question 33

What is the proper syntax for using the or operator?

Answer 33

if (num1 < num2 || num1 > num2)

Question 34

What is the primary use case for switches?

Answer 34

For comparing multiple 1 on 1 values

Question 35

Does the default case have to be at the bottom of the switch statement?

Answer 35

No, default can be anywhere on the list

Question 36

What happens if there is no break statement between cases?

Answer 36

The switch will continue until the next break statement

Question 37

What is an object in JavaScript?

Answer 37

datatype that can hold a group of other data/functions

Question 38

What is a property in relation to JavaScript objects?

Answer 38

It is the key/value data within an object

Question 39

When should you use bracket notation over dot notation with objects?

Answer 39

If you have a regular property name that has characters not valid as a property name. Or substitution of variable names.

Question 40

How do you remove a property from an object?

Answer 40

delete object.property

Question 41

What is an array in JavaScript?

Answer 41

An object that holds a series of data in a list like structure

Question 42

How do you create an array literal?

Answer 42

var array = [ ];

Question 43

What are the keys for the values inside an array?

Answer 43

index numbers starting from 0

Question 44

Arrays have a property named length. Because arrays have a properties, what other data structure are they similar to?

Answer 44

objects

Question 45

What are some good use cases for using objects inside arrays?

Answer 45

A list of people (with their information) | -List of cars

Question 46

What is the primary advantage to storing your selected elements in a variable?

Answer 46

So you don't have to rewrite a lot of code such as "document.getElementById()". You can store it into a variable instead.

Question 47

Why might you need JavaScript to modify the DOM after the page loads?

Answer 47

Dynamic changes to the page according to user input

Question 48

How can you better prepare when writing HTML for DOM manipulation in your JavaScript code?

Answer 48

Use ID's and classes

Question 49

What are the differences between innertext and textContent?

Answer 49

textContent grabs everything, even values that are not visible. innerText only grabs visible text textContent is much faster

Question 50

What datatype are the values you remove from a text input?

Answer 50

string

Question 51

Why is it so important to be able to dynamically update text?

Answer 51

For usability: to allow users to make changes on the website based on their input

Question 52

What are some of the drawbacks of HTML Event Handler Attributes?

Answer 52

Might make the HTML less clear, by adding javascript, instead of keeping them separate Maybe same reason inline styling is bad, using the function for multiple parts of the code

Question 53

What is the difference between the getElementById() method and the querySelector() method?

Answer 53

getElementById() is more specific and quicker. | querySelector() is more broad, general use, and newer, but slightly slower

Question 54

Who passes in the event object into the handleClick callback function?

Answer 54

The javascript engine passes it

Question 55

Does a callback function require a name?

Answer 55

No, you can use an anonymous function

Question 56

What is the purpose of a loop?

Answer 56

Repeat a set of code for a given number of time

Question 57

Why might there be different kinds of loops?

Answer 57

for loops are for incrementing variable. | while loops are for other cases

Question 58

What is the purpose of a conditional expression as it relates to loops?

Answer 58

Lets the loop know when to end, or how long to continue

Question 59

Could a loop potentially go on forever?

Answer 59

Yes, if the condition is never false

Question 60

Could a loop never start?

Answer 60

Yes, if the condition is already false before the loops begins

Question 61

How does a for loop differ from a while loop?

Answer 61

while loops only have a condition in the declaration; | for loops have the incrementation and variable declaration in the

Question 62

What potential use cases are there for for loops?

Answer 62

incrementing, you know how long the loop will go on for

Question 63

Which pieces of information provided in the parentheses for a for loop are mandatory?

Answer 63

for (Initialization; Condition; Final Expression)

Question 64

What is a for in loop?

Answer 64

A variation of a for loop designed for objects. | iterates through each property of the object

Question 65

How do you target the value of a property in an object.

Answer 65

use bracket notation | ex) object[property]

Question 66

What is the difference between the parentNode and parentElement properties?

Answer 66

All elements are nodes, but not all nodes are elements | parentElement ignores whitespace characters

Question 67

What are two ways to target elements on the DOM?

Answer 67

querySelector() | getElementById()

Question 68

What is another way to add a text node to an element other than using textContent.

Answer 68

createTextNode(text)

Question 69

How do you create a HTML element using vanilla Javascript?

Answer 69

createElement() method

Question 70

Why is using loops and arrays for creating multiple dom elements preferable to creating them one at a time?

Answer 70

Much more efficient, less code to write

Question 71

Why are arrays preferred over objects for the functionality referenced in question 1?

Answer 71

arrays have a length property

Question 72

Why is it important to be able to retrieve and use data from inputs?

Answer 72

Handling user input

Question 73

Why is it dangerous to assume you have the correct data when creating elements?

Answer 73

Users can make typos, or enter incorrect information, or HACKERS

Question 74

How would you alter the game to make the choice from 1 - 500?

Answer 74

.

Question 75

What are the disadvantages of inline styling via JavaScript?

Answer 75

.

Question 76

What things do you have to consider when building a reset game function?

Answer 76

.