JavaScript

Question 1

What is the purpose of variables?

Answer 1

variables store primitives like numbers, strings and boolean

Question 2

How do you declare a variable?

Answer 2

var keyword

Question 3

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

Answer 3

equal sign

Question 4

What characters are allowed in variable names?

Answer 4

$, _, letters and digits

Must start with a letter, $ or _

Question 5

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

Answer 5

It means capitalized variable names and non-capitalized variable names are different

Question 6

What is the purpose of a string?

Answer 6

It stores text

Question 7

What is the purpose of a number?

Answer 7

It stores value

Question 8

What is the purpose of a boolean?

Answer 8

It stores true or false

Question 9

What does the = operator mean in JavaScript?

Answer 9

assignment operator

Question 10

How do you update the value of a variable?

Answer 10

use assignment operator again

Question 11

What is the difference between null and undefined?

Answer 11

undefined has been assigned but does not have a value. Null is intentionally left blank.

Question 12

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

Answer 12

for clarity and visibility

Question 13

Give five examples of JavaScript primitives.

Answer 13

numbers, strings, boolean, null and undefined

Question 14

What data type is returned by an arithmetic operation?

Answer 14

number

Question 15

What is string concatenation?

Answer 15

adding strings together

Question 16

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

Answer 16

arithmetic and concatenation

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

addition operator

Question 19

What are objects used for?

Answer 19

To store multiple properties in one variable name

Question 20

What are object properties?

Answer 20

data of the object

Question 21

Describe object literal notation.

Answer 21

starts with variable declaration followed by curly brackets with property names in them.

Question 22

How do you remove a property from an object?

Answer 22

use delete operator

Question 23

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

Answer 23

dot notation or bracket notation

Question 24

What are arrays used for?

Answer 24

To keep lists of data and access them

Question 25

Describe array literal notation.

Answer 25

brackets and data separated by commas

Question 26

How are arrays different from "plain" objects?

Answer 26

They are in order and indexed

Question 27

What number represents the first index of an array?

Answer 27

zero

Question 28

What is the length property of an array?

Answer 28

it returns how many data are inside the array

Question 29

How do you calculate the last index of an array?

Answer 29

subtract one from the length of the array since it starts at zero

Question 30

What is a function in JavaScript?

Answer 30

Reusable code block

Question 31

Describe the parts of a function definition.

Answer 31

function name, parameter, code block

Question 32

Describe the parts of a function call.

Answer 32

functionName(argument)

Question 33

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

Answer 33

call is using arguments and definition is using parameters

Question 34

Why are function parameters useful?

Answer 34

Because unlike constant values, we can make changes to that one parameter and rest of the code block will change

Question 35

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

Answer 35

It returns a value and executes the function

Question 36

Why do we log things to the console?

Answer 36

To debug and for data accuracy

Question 37

What is a method?

Answer 37

Method is a function that is a property of an object

Question 38

How is a method different from any other function?

Answer 38

It is exclusive to the object

Question 39

How do you remove the last element from an array?

Answer 39

pop() method of array object

Question 40

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

Answer 40

floor) method of Math object

Question 41

How do you generate a random number?

Answer 41

random() method of Math object

Question 42

How do you delete an element from an array?

Answer 42

Either shift() or splice() method of array object

Question 43

How do you append an element to an array?

Answer 43

push() method of array object

Question 44

How do you break a string up into an array?

Answer 44

split() method of string object

Question 45

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

Answer 45

No it does not. Use console log to check.

Question 46

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

Answer 46

A lot. Maybe like 20 to 30.

Question 47

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

Answer 47

No

Question 48

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

Answer 48

A lot. Maybe like 20 to 30.

Question 49

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

Answer 49

MDN

Question 50

What is the purpose of an if statement?

Answer 50

Decision making

Question 51

What are the three logical operators?

Answer 51

And, Or, Not

Question 52

What is the purpose of a loop?

Answer 52

To repeat our desired action

Question 53

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

Answer 53

To eventually stop the loop from running forever

Question 54

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

Answer 54

To repeat things easily

Question 55

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

Answer 55

Before each repetition starts

Question 56

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

Answer 56

At the beginning of for loop (only once)

Question 57

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

Answer 57

Before each repetition starts

Question 58

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

Answer 58

At the end of each repetition

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

break statement

Question 60

What does the ++ increment operator do?

Answer 60

Increments by 1 and updates

Question 61

How do you iterate through the keys of an object?

Answer 61

use for in loop (var in object)