javascript

Question 1

What is the purpose of variables?

Answer 1

Store data and information.

Question 2

How do you declare a variable?

Answer 2

Start with a variable keyword, followed by the variable name and followed by a semicolon.

Question 3

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

Answer 3

use an assignment operator (=)

Question 4

What characters are allowed in variable names?

Answer 4

a-z(case sensitive), _(underscore), dollar sign, camel case, numbers.

Question 5

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

Answer 5

App vs app means two different variables.

Question 6

What is the purpose of a string?

Answer 6

Store text data and They are frequently used to add
new content into a page and they
can contain HTML markup.

Question 7

What is the purpose of a number?

Answer 7

Calculating.  determining the size of the
screen, moving the position of
an element on a page, or setting
the amount of time an element
should take to fade in.

Question 8

What is the purpose of a boolean?

Answer 8

true or false.

Question 9

What does the = operator mean in JavaScript?

Answer 9

assign the value

Question 10

How do you update the value of a variable?

Answer 10

assign another value?

Question 11

What is the difference between null and undefined?

Answer 11

null is an assigned value, undefined means there is a declared available but not defined.

Question 12

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

Answer 12

It will be easier to locate the data you are looking for.

Question 13

Give five examples of JavaScript primitives.

Answer 13

string, number, boolean, undefined, and null.

Question 14

What are objects used for?

Answer 14

store data

Question 15

What are arrays used for?

Answer 15

store a collection of data such as lists

Question 16

What number represents the first index of an array?

Answer 16

0

Question 17

What is the length property of an array?

Answer 17

the name of the array.length

Question 18

What is a function in JavaScript?

Answer 18

A block of code that can be stored and reused.

Question 19

What is the difference between a parameter and an argument?

Answer 19

the parameter is the name and the argument is the real value.

Question 20

Why are function parameters useful?

Answer 20

It can store different types of data.

Question 21

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

Answer 21

no code will be run after the return statement.

Question 22

Why do we log things to the console?

Answer 22

Console log provides you data and checks things work correctly.

Question 23

What is a method?

Answer 23

is a function?

Question 24

How is a method different from any other function?

Answer 24

need to look up.

Question 25

How do you remove the last element from an array?

Answer 25

pop()

Question 26

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

Answer 26

math.floor()

Question 27

How do you generate a random number?

Answer 27

math.random()

Question 28

How do you delete an element from an array?

Answer 28

splice()

Question 29

How do you append an element to an array?

Answer 29

push(), unshift()

Question 30

How do you break a string up into an array?

Answer 30

split(“ “)

Question 31

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

Answer 31

You cannot change the original string.

Question 32

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

Answer 32

roughly 30 methods.

Question 33

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

Answer 33

They are not always useful. Sometimes the return value does not give you much information.

Question 34

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

Answer 34

a lot of them

Question 35

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

Answer 35

MDN

Question 36

Why do we log things to the console?

Answer 36

To test the code runs properly.

Question 37

What is a “model”?

Answer 37

?

Question 38

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

Answer 38

html?

Question 39

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

Answer 39

elements in the html

Question 40

What is a DOM Tree?

Answer 40

The structure of the html?

Question 41

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

Answer 41

queryselector()

Question 42

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

Answer 42

queryselectorAll()

Question 43

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

Answer 43

easily to locate?

Question 44

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

Answer 44

console.dir()

Question 45

Why would a tag need to be placed at the bottom of the HTML content instead of at the top?

Answer 45

The browser needs to parse all of the elements in the HTML page before the JavaScript code can access them.

Question 46

What does document.querySelector() take as its argument and what does it return?

Answer 46

CSS selector.