javascripot

Question 1

What is the purpose of variables?

Answer 1

to store values

Question 2

How do you declare a variable?

Answer 2

var name

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

period, undrescore, characters $#@, and letters

Question 5

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

Answer 5

a capital letter changes the variable, different variable

Question 6

What is the purpose of a string?

Answer 6

store characters

Question 7

What is the purpose of a number?

Answer 7

numerical value to math or store

Question 8

What is the purpose of a boolean?

Answer 8

gives true/false values

Question 9

What does the = operator mean in JavaScript?

Answer 9

assign value

Question 10

How do you update the value of a variable?

Answer 10

assign a new value to the variable

Question 11

What is the difference between null and undefined?

Answer 11

null is intentionally undefined, undefined was just never given any value

Question 12

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

Answer 12

so you know what is logging what in longer code.

Question 13

Give five examples of JavaScript primitives.

Answer 13

undefined, null, boolean, string and number

Question 14

What data type is returned by an arithmetic operation?

Answer 14

number

Question 15

What is string concatenation?

Answer 15

appending a string onto another string

Question 16

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

Answer 16

arithmetic addition and string 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

sets the value to the value plus the number

Question 19

What are objects used for?

Answer 19

groups set of variables and functions to create a model of something

Question 20

What are object properties?

Answer 20

a variable that is part of an object

Question 21

Describe object literal notation.

Answer 21

setting a var object = {}

Question 22

How do you remove a property from an object?

Answer 22

using the delete keyword

Question 23

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

Answer 23

dot notation and bracket notation

Question 24

What are arrays used for?

Answer 24

set of values related to each other, a list

Question 25

Describe array literal notation.

Answer 25

var array = []

Question 26

How are arrays different from "plain" objects?

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

How many values are int he array

Question 29

How do you calculate the last index of an array?

Answer 29

.lenght-1

Question 30

What is a function in JavaScript?

Answer 30

set of code that takes arguments and can be called

Question 31

Describe the parts of a function definition.

Answer 31

``` function operator-name of function(parameters) { } ```

Question 32

Describe the parts of a function call.

Answer 32

function(arguments);

Question 33

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

Answer 33

function definition uses function keyword, calling uses the function name and arguments.

Question 34

What is the difference between a parameter and an argument?

Answer 34

parameters are placeholders that can store arguments.

Question 35

Why are function parameters useful?

Answer 35

Makes functions reusable with different arguments.

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 we can use in our program. Prevents any more code in the function's code block from being run.

Question 37

Why do we log things to the console?

Answer 37

Check console output to see where we are in code and for errors

Question 38

What is a method?

Answer 38

a function which is a property of an object

Question 39

How is a method different from any other function?

Answer 39

it is associated with an object

Question 40

How do you remove the last element from an array?

Answer 40

.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

.splice

Question 44

How do you append an element to an array?

Answer 44

.push or .unshift or .splice(0 placement appended)

Question 45

How do you break a string up into an array?

Answer 45

.split

Question 46

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

Answer 46

no. console.log the string before and after the method

Question 47

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

Answer 47

~30

Question 48

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

Answer 48

no. push, unshift return length of array- splice returns spliced element.

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

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

Answer 50

~30

Question 51

Give 6 examples of comparison operators.

Answer 51

great, less than, greater =, lesser =, equal to, not equal to, strictly equal to

Question 52

What data type do comparison expressions evaluate to?

Answer 52

boolean

Question 53

What is the purpose of an if statement?

Answer 53

determines execution path based on a condition

Question 54

Is else required in order to use an if statement?

Answer 54

No

Question 55

Describe the syntax (structure) of an if statement.

Answer 55

if (condition) { code };

Question 56

What are the three logical operators?

Answer 56

&&, ||, !

Question 57

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

Answer 57

if else

Question 58

What is the purpose of a loop?

Answer 58

to reiterate code during a condition

Question 59

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

Answer 59

to tell the loop when to stop iterating

Question 60

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

Answer 60

one time through the loop

Question 61

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

Answer 61

at the beginning before code block runs.

Question 62

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

Answer 62

at the start once before iteration

Question 63

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

Answer 63

after initialization and before the code runs

Question 64

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

Answer 64

before the condition expression.

Question 65

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

Answer 65

break.

Question 66

What does the ++ increment operator do?

Answer 66

adds 1

Question 67

How do you iterate through the keys of an object?

Answer 67

for in loop

Question 68

What is a method?

Answer 68

function which is a property of an object.

Question 69

How can you tell the difference between a method definition and a method call?

Answer 69

call is object.methodname definition is methodname: function ()

Question 70

Describe method definition syntax (structure).

Answer 70

``` var object = { methodname: function(){ } } ```

Question 71

Describe method call syntax (structure).

Answer 71

object.methodname

Question 72

How is a method different from any other function?

Answer 72

tied to an object

Question 73

What is the defining characteristic of Object-Oriented Programming?

Answer 73

based on objects and procedures

Question 74

What are the four "principles" of Object-Oriented Programming?

Answer 74

Abstraction Encapsulation Inheritance Polymorphism

Question 75

What does API stand for?

Answer 75

Application programming interface

Question 76

What is the purpose of an API?

Answer 76

simplify for users

Question 77

What is this in JavaScript?

Answer 77

this keyword refers to an object. | this is an implicit parameter of all JavaScript functions.

Question 78

What does it mean to say that this is an "implicit parameter"?

Answer 78

parameter not explicitly defined

Question 79

When is the value of this determined in a function; call time or definition time?

Answer 79

call time

Question 80

``` What does this refer to in the following code snippet? var character = { firstName: 'Mario', greet: function () { var message = 'It\'s-a-me, ' + this.firstName + '!'; console.log(message); } }; ```

Answer 80

Mario

Question 81

Given the above character object, what is the result of the following code snippet? Why? character.greet();

Answer 81

It's a me Mario! | because the this.firstName calls the character object to fill the statement

Question 82

``` Given the above character object, what is the result of the following code snippet? Why? var hello = character.greet; hello(); ```

Answer 82

undefined

Question 83

How can you tell what the value of this will be for a particular function or method definition?

Answer 83

it is defined at definition

Question 84

How can you tell what the value of this is for a particular function or method call?

Answer 84

the value of this can be recognized as "the object to the left of the dot" when the function is called (as a method).