JS

Question 1

What is a variable?

Why are variables useful?

Answer 1

container that stores information such as strings, numbers, booleans etc

They are able to be reused and reassigned to a value; concise for readability

Question 2

How do you declare a variable?

How do you assign a value to a variable?

Answer 2

var ( keyword ) = name( value )

( = ) assignment operator

Question 3

What is a string?

What is the string concatenation operator?

Answer 3

0 or more characters inside quotes.
it is the data type stored in quotes

(+) Adds the first and second string together

Question 4

How do you escape quotation characters?

Answer 4

( \ ) As a character to prevent interpreting a quote as the end of a string

Question 5

What is type coercion?

Answer 5

Is the process of converting a value from one to another.

ex: number will become a string with concatenation

Question 6

What is a number in JavaScript?

Answer 6

A primitive data type by literals

Question 7

What is an arithmetic operator?

Name four of the arithmetic operators?

Answer 7

operator and operand; anything that can do math

+,-,*, /

Question 8

What is a boolean?

Answer 8

Variable that can only have a value of true or false

Question 9

What is a comparison operator?

Answer 9

=== ; same type and same content

Question 10

What is the difference between undefined and null?

Answer 10

undefined: variable declared. but no value, it is default.
null: object, is an assignment value of nothing, needs to be set to Null. (assigned on purpose)

Question 11

What is a function and why are they useful?

Answer 11

A function is a set of statements that perform a task. Functions are useful because they are expressions that can have a return value

Question 12

How do you call a function?

What are the parts of a function definition?

Answer 12

function name(parameter ) {
}

function keyword , function name , (parameters) {
code block
}

Question 13

What is the difference between a parameter and an argument?

Answer 13

Parameter: Space prepared for data; variable in method definition

Argument: Value that goes into the variable. Data that is passed through parameters.

Question 14

Why is it important to understand truthy and falsy values?

Answer 14

allow use the ability to use conditionals.

Question 15

Falsy Values

Answer 15

if (false)
if (null)
if (undefined)
if (0)
if (-0)
if (0n)
if (NaN)
if ("")

Question 16

Truthy Values

Answer 16

if (true)
if ({})
if ([])
if (42)
if ("0")
if ("false")
if (new Date())
if (-42)
if (12n)
if (3.14)
if (-3.14)
if (Infinity)
if (-Infinity)

Question 17

Logical Operators:
and
or
not

Answer 17

&&
||
!

Question 18

What happens if there is no break statement between cases?

Answer 18

It will fall through. it’ll run cases that fall below.

instead of switch statements, a conditional can be written.

Question 19

What is an object in JavaScript?

Answer 19

data type that stores data

Question 20

How do you create an object literal?

Answer 20

var keyword = { }

Question 21

What is a property in relation to JavaScript objects?

Answer 21

it is a key-value pair

Question 22

Dot notation?

Answer 22

object.property = value;

Question 23

Bracket Notation?

Answer 23

object[‘property’] = ‘value’;

Question 24

What is an array in JavaScript?

How do you create an array literal?

Answer 24

variable that stores a list of values

var arr = [ ‘one’, ‘two’, ‘three’]

Question 25

What are the keys for the values inside an array?

Answer 25

Name of the Array & Value of the array

Question 26

DOM Manip 1

What is the primary advantage to storing your selected elements in a variable?

Answer 26

if you are planning to use it multiple times

Question 27

DOM Man 2

Why use .textContent?

Answer 27

collects and updates JUST the text.

Question 28

Why is it so important to be able to dynamically update text?

Answer 28

So the website can be more responsive to the user

Question 29

What datatype are the values you remove from a text input?

Answer 29

from a text input, we will always pull out a string.

Question 30

What is the difference between the getElementById() method and the querySelector() method?

Answer 30

id = HTML ID

querySelector = class or element

Question 31

Does a callback function require a name?

Answer 31

No, they can be anonymous

Question 32

What is the purpose of a loop?

Answer 32

Allows you to repeat an action; checking conditionals

Question 33

What is the purpose of a conditional expression as it relates to loops?

Answer 33

Gives the ability to start, stop, and implement the while loop

Question 34

How does a for loop differ from a while loop?

Answer 34

For: Already know how many times to execute
While: Don’t know how many times they will run

Question 35

Which pieces of information provided in the parentheses for a for loop are mandatory?

Answer 35

for (let i = 0; i < 9; i++) {
  codeblock;
}

Question 36

What is a for in loop?When is it good to use?

Answer 36

for loop that iterates through an object; object literal

Question 37

How do you target a value of a property in an object?

Answer 37

using bracket notation.

Question 38

What is the difference between the parentNode and parentElement properties?

Answer 38

parentNode: Finds elements for containing elements in HTML

**parentElement: Returns NULL when HTML doesnt have a parent element node.

Question 39

Why is it important to be able to traverse the DOM?

Answer 39

You have the ability to select other elements in regards to the
(parent, sibling, and child)

Question 40

What are two ways to target elements on the DOM?

Answer 40

• querySelector

- getElementbyId

Question 41

What is another way to add a text node to an element other than using .textContent?

Answer 41

.createTextNode( )

Question 42

How do you create a HTML element using vanilla Javascript?

Answer 42

document.createElement(‘ ‘)

Question 43

Why is using loops and arrays for creating multiple dom elements preferable to creating them one at a time?

Answer 43

Faster and more efficient. It is much more concise with a loop.

Question 44

Why are arrays preferred over objects for the functionality ?

Answer 44

Arrays are indexed. You are able to control what you are able to use in terms of DOM Creation

Question 45

Why is it important to be able to retrieve and use data from inputs?

Answer 45

Gathering user input in general.

Question 46

Why is it dangerous to assume you have the correct data when creating elements?

Answer 46

Your code may not be responsive. It can cause user to make problems into the input

Question 47

JS oop 5

What is the first thing that happens in a class when it is instantiated with the ‘new’ keyword

Answer 47

An empty object is created

Question 48

JS OOP5

Since classes are technically classes. Can you name a difference between classes and functions?

Class*constructor

Answer 48

Classes use a ‘new’ keyword.
‘new’ keyword makes an object.

Functions you can call with ( )

Question 49

What is a static method?

Answer 49

Methods attached to the creator object.

- use it off of the creator not the object itself

Question 50

Variables defined with the var keyword are function scoped. const and let are _____ scoped.

Answer 50

block scoped

Question 51

Name some characteristics of a variable declared using const.

Answer 51

cannot be hoisted

Question 52

Name some characteristics of a variable declared using let.

Answer 52

cannot be hoisted

Question 53

What does block scoped mean?

Answer 53

By the closest { }

Question 54

In the file we can push a new value to an array defined using the const variable. How does that work?

Answer 54

you are modifying the reference data type in memory, not the actual variable

Question 55

Name some things that var can do that const and let can’t.

Answer 55

var can be hoisted, becomes a property of the window object. Can be redeclared and reassigned.