JavaScript

Question 1

What is the purpose of variables

Answer 1

To store info to use later

Question 2

How do you declare a variable?

Answer 2

let or var

Question 3

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

Answer 3

=

Question 4

What characters are allowed in variable names?

Answer 4

Letters, Numbers, $, _

can’t start with numbers

Question 5

variables are case sensitive

Answer 5

True

Question 6

Purpose of strings?

Answer 6

store text

Question 7

purpose of numbers?

Answer 7

calculations or adjusting CSS

Question 8

purpose of a boolean?

Answer 8

true or false

Question 9

what does the = operator mean?

Answer 9

assignment

Question 10

how do you update the value of a variable?

Answer 10

variable name = new value

Question 11

null vs undefined?

Answer 11

Nulls are set intentionally by the developer, whereas undefined is set by JS.
Null may indicate that a value will be assigned eventually.

Question 12

Why is it a good habit to include “labels” when logging values.

Answer 12

Good for debugging.

Question 13

5 examples of JS Primitives

Answer 13

String, number, Boolean, undefined, null

Question 14

What data type is returned by an arithmetic operation?

Answer 14

number

Question 15

What is string concatenation?

Answer 15

combining strings together into a new string

Question 16

What purpose does the + plus operator serve in JavaScript?

Answer 16

Adds numbers together or concatenating strings

Question 17

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

Answer 17

Boolean

Question 18

What does += do?

Answer 18

Adds a value onto a variable, and then stores that new value into the same variable.

Question 19

Operant

Answer 19

Value that an operator is operating on

Question 20

What are objects used for?

Answer 20

Grouping data that are related to eachother

Question 21

What are object properties?

Answer 21

variables in an object

Question 22

Describe object literal notation

Answer 22

Key value pairs separated by commas, stored between two curly brackets, and is assigned to a variable. Keys and values are separated with a colon.

Question 23

How do you remove a property from an object?

Answer 23

Delete operator then use dot notation to choose the property or method

Question 24

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

Answer 24

Dot notation or bracket

Question 25

What are arrays used for?

Answer 25

Storing information that is related with each other with an order. Also used when you don't know how much space you need.

Question 26

Describe array literal notation.

Answer 26

Values separated by commas within square brackets and then assigned to a variable.

Question 27

How are arrays different from "plain" objects?

Answer 27

The key is an index number.

Question 28

What number represents the first index of an array?

Answer 28

0

Question 29

What is the length property of an array?

Answer 29

Tells you how many items is in the array.

Question 30

How do you calculate the last index of an array?

Answer 30

You subtract one from the length of the array.

Question 31

Why do we log things to the console?

Answer 31

debugging and verification

Question 32

what is a method?

Answer 32

A function that is a property of an object.

Question 33

How is a method different from any other function?

Answer 33

properties of an object | you can also work with other data part of that object

Question 34

how do you remove the last element from an array

Answer 34

pop

Question 35

how do you round a number down to the nearest integer

Answer 35

Math.floor()

Question 36

how do you generate a random number?

Answer 36

Math.random()

Question 37

How do you delete an element from an array?

Answer 37

Splice, pop, shift

Question 38

How do you break a string up into an array

Answer 38

.split()

Question 39

Do string methods change the original string?

Answer 39

No

Question 40

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

Answer 40

~40

Question 41

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

Answer 41

~30

Question 42

Use MDN

Answer 42

Use MDN

Question 43

Give 6 examples of comparison operators.

Answer 43

``` === >= <= > < !== ```

Question 44

What data type do comparison expressions evaluate to?

Answer 44

Boolean

Question 45

What is the purpose of an if statement?

Answer 45

Decisions

Question 46

Is else required in order to use an if statement?

Answer 46

No

Question 47

Describe the syntax of an if statement

Answer 47

``` conditional statement (condition in parenthesis ) { code block in curly brackets } other conditionals statements if necessary ```

Question 48

What are the three logical operators?

Answer 48

&&, ||, !

Question 49

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

Answer 49

logical operators

Question 50

What is the purpose of a loop?

Answer 50

To run a set of code one or more times

Question 51

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

Answer 51

Tells the loop when to run the code. | Provides a stopping point.

Question 52

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

Answer 52

It is every time you run through a loop code block.

Question 53

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

Answer 53

It happens before each iteration.

Question 54

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

Answer 54

It is the first thing that happens.

Question 55

When does the condition of a for loop get evaluated?

Answer 55

It gets evaluated before each iteration.

Question 56

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

Answer 56

It gets evaluated after each iteration.

Question 57

Besides return, what keyword exits a function block?

Answer 57

break

Question 58

What does the ++ increment operator do?

Answer 58

adds one

Question 59

how do you iterate through keys of an object?

Answer 59

for in loop