JAVASCRIPT

Question 1

What is the purpose of variables?

Answer 1

store data

Question 2

How do you declare a variable?

Answer 2

var let const

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

number, letter, underscore, $

Question 5

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

Answer 5

lowercase and uppercase matters

Question 6

What is the purpose of a string?

Answer 6

store letters

Question 7

What is the purpose of a number?

Answer 7

store numerical data

Question 8

What is the purpose of a boolean?

Answer 8

true/false used to make decisions

Question 9

What does the = operator mean in JavaScript?

Answer 9

assign

Question 10

How do you update the value of a variable?

Answer 10

reassign a new value

Question 11

What is the difference between null and undefined?

Answer 11

undefined: no value assigned
null: set to nothing

Question 12

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

Answer 12

to know what you are actually logging

Question 13

Give five examples of JavaScript primitives.

Answer 13

number, string, boolean, null, undefined

Question 14

What data type is returned by an arithmetic operation?

Answer 14

number

Question 15

What is string concatenation?

Answer 15

combining strings

Question 16

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

Answer 16

addition of numbers and concatenation of 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

assigns the value of the variable to the previous value plus right-side of operator

Question 19

What are objects used for?

Answer 19

store multiple types of data that are related

Question 20

What are object properties?

Answer 20

variables glued to objects

Question 21

Describe object literal notation.

Answer 21

{key: value}

Question 22

How do you remove a property from an object?

Answer 22

delete operator

Question 23

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

Answer 23

object.property (dot notation)

object[‘property’] (square bracket notation)

Question 24

What are arrays used for?

Answer 24

store data in order

Question 25

Describe array literal notation.

Answer 25

var array = [ ]

Question 26

How are arrays different from "plain" objects?

Answer 26

numeric indexes vs named properties | arrays have order

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

number of items in the array

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 performs a task or calculates a value

Question 31

Describe the parts of a function definition.

Answer 31

1. function keyword 2. optional name 3. zero or more parameters in ( ) separated by commas 4. code block { } 5. optional return statement inside code block

Question 32

Describe the parts of a function call.

Answer 32

1. functions name | 2. zero or more arguments in ( ) separated by commas

Question 33

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

Answer 33

function calls do not have code blocks or keyword

Question 34

What is the difference between a parameter and an argument?

Answer 34

parameters are placeholders in a function definition | arguments are actual data in a function call

Question 35

Why are function parameters useful?

Answer 35

reusability and variability

Question 36

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

Answer 36

causes the function to produce a value | also exits the function; no code after the return statement is executed

Question 37

Why do we log things to the console?

Answer 37

so we can keep track of our data as we change it

Question 38

What is a method?

Answer 38

a function

Question 39

How is a method different from any other function?

Answer 39

function which is a property of an object, static and instance

Question 40

How do you remove the last element from an array?

Answer 40

array.pop( )

Question 41

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

Answer 41

Math.floor( )

Question 42

How do you generate a random number?

Answer 42

Math.random( )

Question 43

How do you delete an element from an array?

Answer 43

array. pop( ) end array. shift( ) start array. splice( ) anywhere

Question 44

How do you append an element to an array?

Answer 44

array. push( ) end | array. unshift( ) start

Question 45

How do you break a string up into an array?

Answer 45

string.split( )

Question 46

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

Answer 46

no. log to console before and after method

Question 47

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

Answer 47

no

Question 48

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

Answer 48

MDN

Question 49

Give 6 examples of comparison operators.

Answer 49

, <=, >=, ==, ===

Question 50

What data type do comparison expressions evaluate to?

Answer 50

boolean

Question 51

What is the purpose of an if statement?

Answer 51

to make decisions

Question 52

Is else required in order to use an if statement?

Answer 52

no

Question 53

Describe the syntax (structure) of an if statement.

Answer 53

if (condition) {codeblock}

Question 54

What are the three logical operators?

Answer 54

&&AND ||OR !NOT

Question 55

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

Answer 55

$$ ||

Question 56

What is the purpose of a loop?

Answer 56

to repeat the same, or similar, code a number of times

Question 57

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

Answer 57

to stop the loop

Question 58

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

Answer 58

each time the loop runs

Question 59

When does the condition expression of a loop get evaluated?

Answer 59

before each iteration

Question 60

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

Answer 60

once, when the loop begins

Question 61

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

Answer 61

after each iteration

Question 62

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

Answer 62

break

Question 63

What does the ++ increment operator do?

Answer 63

increments (adds one to) its operand and returns a value

Question 64

How do you iterate through the keys of an object?

Answer 64

for in loop

Question 65

In JavaScript, when is a function's scope determined; when it is called or when it is defined?

Answer 65

defined

Question 66

What allows JavaScript functions to "remember" values from their surroundings?

Answer 66

closures