JavaScript

Question 1

What is the purpose of variables?

Answer 1

to store data

Question 2

How do you declare a variable?

Answer 2

use keyword “var”

Question 3

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

Answer 3

var variable = something

Question 4

What characters are allowed in variable names?

Answer 4

letter, digits, underscore, dollar signs

Question 5

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

Answer 5

they must be recalled exactly as they were saved

Question 6

What is the purpose of a string?

Answer 6

store and manipulate text

Question 7

What is the purpose of a number?

Answer 7

store and manipulate data

Question 8

What is the purpose of a boolean?

Answer 8

to register something as true or false

Question 9

What does the = operator mean in JavaScript?

Answer 9

it is assigning a value to a variable name

Question 10

What is the difference between null and undefined?

Answer 10

null is intentionally given a non-existing value, undefined unintentionally lacks a value

Question 11

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

Answer 11

so that you have a better idea of what issues may have occurred when debugging

Question 12

Give five examples of JavaScript primitives.

Answer 12

string, number, boolean, undefined, null

Question 13

to update a variable

Answer 13

use variable followed by value… don’t need to use ‘var’ again

Question 14

What data type is returned by an arithmetic operation?

Answer 14

a number

Question 15

What is string concatenation?

Answer 15

the combining of two or more strings

Question 16

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

Answer 16

it adds a value to another variable/value

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

adds a value to a variable and re-assigns the variable

Question 19

What are objects used for?

Answer 19

group together set of variables and functions

Question 20

What are object properties?

Answer 20

a variable within an object

Question 21

Describe object literal notation.

Answer 21

a saved variable followed by curly brace with key-value properties and methods (functions)

Question 22

How do you remove a property from an object?

Answer 22

delete then object.property

Question 23

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

Answer 23

either dot or bracket notation

Question 24

What are arrays used for?

Answer 24

storing a list of values

Question 25

Describe array literal notation.

Answer 25

var name = [skhf,fskdjhf,skdjfh]

Question 26

How are arrays different from "plain" objects?

Answer 26

do not use colons, do not use curly braces, etc arrays are indexed, objects aren't

Question 27

What number represents the first index of an array?

Answer 27

0

Question 28

What is the length property of an array?

Answer 28

array.length... tells you how many items are listed

Question 29

How do you calculate the last index of an array?

Answer 29

array.length - 1

Question 30

What is a function in JavaScript?

Answer 30

a set of statements that perform a task or calculate a value based off their parameters, and code block

Question 31

Describe the parts of a function definition.

Answer 31

parts of a function definition include function name, parameters/arguments, curly brace, optional return statement, and the code

Question 32

Describe the parts of a function definition.

Answer 32

parts of a function definition include function name, parameters/arguments, curly brace, optional return statement, and the code

Question 33

Describe the parts of a function call.

Answer 33

functionName(optional arguments)

Question 34

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

Answer 34

no function key word and no brackets in function call... definition does have it

Question 35

What is the difference between a parameter and an argument?

Answer 35

parameter has no value while argument does

Question 36

Why are function parameters useful?

Answer 36

to tell you what type of value to input into a function

Question 37

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

Answer 37

stops the code from running any longer, causes function to produce a value we can use in our program

Question 38

Why do we log things to the console?

Answer 38

so that we can see the output of our code and make sure things are functioning properly

Question 39

What is a method?

Answer 39

a function which is a property of an object.... essentially a built in function

Question 40

How is a method different from any other function?

Answer 40

property of an object while other functions are hanging in space

Question 41

How do you remove the last element from an array?

Answer 41

.pop() method

Question 42

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

Answer 42

Math.floor() method

Question 43

How do you generate a random number?

Answer 43

Math.random() method

Question 44

How do you delete an element from an array?

Answer 44

.splice(1,0) method

Question 45

How do you append an element to an array?

Answer 45

.push() method

Question 46

How do you break a string up into an array?

Answer 46

.split() method

Question 47

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

Answer 47

no, you assign the value of the string method response to a new variable and call the original string if you want to see it

Question 48

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

Answer 48

Around 50

Question 49

roughly how many array methods are there according to the MDN web docs

Answer 49

40-50

Question 50

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

Answer 50

MDN

Question 51

is a return value useful in every situation

Answer 51

not necessarily, you might just pop something off an array and thats it

Question 52

Give 6 examples of comparison operators.

Answer 52

< > <= >= != = ===etc

Question 53

What data type do comparison expressions evaluate to?

Answer 53

booleans (true or false)

Question 54

What is the purpose of an if statement?

Answer 54

if that condition is met, then run the following code

Question 55

Is else required in order to use an if statement?

Answer 55

no

Question 56

Describe the syntax (structure) of an if statement.

Answer 56

if keyword followed by parentheses, rule, curly brace, code

Question 57

What are the three logical operators?

Answer 57

"and" "or", and "not"

Question 58

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

Answer 58

have both expressions in the same parenthesis

Question 59

What is the purpose of a loop?

Answer 59

run repeated code under specific conditions

Question 60

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

Answer 60

tells you requirements on if the loop should run and how long the loop should be run

Question 61

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

Answer 61

each "time" the code is executed

Question 62

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

Answer 62

beginning of each iteration

Question 63

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

Answer 63

the start of the loop

Question 64

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

Answer 64

after initialization at first, then after every iteration

Question 65

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

Answer 65

after the iteration

Question 66

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

Answer 66

break keyword

Question 67

What does the ++ increment operator do?

Answer 67

increments by 1

Question 68

How do you iterate through the keys of an object?

Answer 68

for-in loop

Question 69

Why do we log things to the console?

Answer 69

so that we can see the output of our actions

Question 70

What is a "model"?

Answer 70

recreation of something

Question 71

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

Answer 71

the html document

Question 72

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

Answer 72

every tree node... the separate parts of the html

Question 73

What is a DOM Tree?

Answer 73

a layout of all html objects

Question 74

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

Answer 74

document.getElementById() document.querySelector()

Question 75

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

Answer 75

document.getElementsByClassName() document.querySelectorAll()

Question 76

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

Answer 76

so that you can call that variable and change another attribute about it.... or just to refer back to it

Question 77

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

Answer 77

console.dir()

Question 78

Why would a