Arrays

Question 1

What is an array?

Answer 1

Array ares a data structure.

Way store and organize data

Question 2

Why are arrays better than variables?

Answer 2

Variables store strings, numbers, and booleans.

Variables can store single value only– which is limiting.

Question 3

What types of data can arrays hold?

Answer 3

Strings

Numbers

Booleans

Even Other Arrays

Question 4

What are 2 practical examples where arrays can be used?

Answer 4

Shopping list

Online order list

Question 5

What’s the syntax of an array?

Answer 5

variable name = [];

Question 6

What symbol do you use to separate list values?

Answer 6

commas

Question 7

Does the last value in the list of array items have a comma?

Answer 7

No

Question 8

Why should you breakup items?

Answer 8

Easier to read

Easier to edit

Question 9

What is zero index?

Answer 9

The counting starts at 0.

Rather than at 1

First item is at 0 index.

Second item is at 1 index.

Third item is at 2 index.

Question 10

What symbol do you use to return values?

Answer 10

[]

brackets

Question 11

What happens if you list an item not on the list?

Example [4]

Answer 11

Last item is undefined in console because nothing in index 4.

Question 12

script.js contains an array of string values (the names of players in a game). Practice using array indices by accessing individual names in the players array. Start by logging the first name inside the array using the console.log() method.

First Response:

const players = [‘Toni’, ‘Anwar’, ‘Mali’, ‘Carlos’, ‘Cormac’, ‘Sariah’];

Answer 12

Notice the syntax:

Parenthesis

variable name

Brackets

;

Question 13

Complete the code below to log the message “Arrays are awesome” to the console:

Answer 13

Question 14

Arrays are zero-based. What does that mean?

Answer 14

The index of the first element inside an array is 0 (not 1).

Question 15

Which of the following best describes an array?

Answer 15

A collection of values you can assign to a single variable.

Question 16

In this array, which code snippet prints the number 1 to the JS console?

Answer 16

Question 17

What’s a great resource for JS?

Answer 17

MDN

Mozilla Developer Network

Question 18

What does the length property do?

Answer 18

returns values in array

number of items in array

Question 19

How do you add elements?

Answer 19

Use .push to add to the end of the array.

Use .unshift to the beginning of the array

Question 20

What does .push do?

Answer 20

Adds elements

Adds to the end of an array

Question 21

What does .unshift do?

Answer 21

.unshift adds an element to the beginning of an array

Question 22

The array assigned to the guestList variable holds a list of names. Add two new names to the end of the array using the push() method. Make sure not to type the names directly inside the guestList array 😁.

Answer 22

variableName.push(‘Name1’, ‘Name2’);

Question 23

Now add two names to the beginning of the array using the .unshift array method

Answer 23

Question 24

How do you remove elements from an array?

Answer 24

.pop and .shift methods remove items from an array

Question 25

How does the .pop method remove items?

Answer 25

.pop takes off the last item from the array

Question 26

How does the .shift method remove elements?

Answer 26

Takes first item off from an array

Question 27

How do you remove tuna from the list?

Answer 27

let [new variable name] = [variableWithList].shift();

Question 28

What methods help create first in, first out?

Answer 28

.Push and .shift method work together:

Question 29

What happens if you write numbers.length given this array?

Answer 29

It returns the length of 5

Question 30

What happens if you apply numbers.push(600)?

Answer 30

Adds 600 to the const numbers array .push adds to the end of an array

Question 31

What happens if you apply numbers.unshift(0)?

Answer 31

You add 0 to beginning of an array

Question 32

What happens if you apply numbers.shift()

Answer 32

Returns 0

Question 33

The array assigned to the variable orderQueue contains a list of order numbers. Declare a new variable named shipping. Remove the first element from the orderQueue array and assign it to the shipping. variable.

Answer 33

Question 34

Next, declare a new variable named cancelled. Remove the last item from the orderQueue array and assign it to the variable cancelled. Use the array that method removes the last element from an array and returns it.

Answer 34

.pop() returns last value removes last value

Question 35

What is the spread operator look like?

Answer 35

3 dots + variable name

Question 36

What does the spread operator do?

Answer 36

The spread operator (...) a JS syntax that builds, combines, and manipulate arrays quickly and seamlessly.

Question 37

How do you connect HTML and JS file?

Answer 37

Add a JS script tag to the index.html

Question 38

What is a two-dimensional array?

Answer 38

It's an array within an array.

Question 39

How do you connect arrays with the spread operator?

Answer 39

You use the 3 dots and variable name Example ...middle

Question 40

How do you bring together two arrays into a new variable altogether?

Answer 40

Use spread operators ... with variable names

Question 41

How would you remove an array?

Answer 41

Use woodwind.pop() It would only remove from woodwind array

Question 42

How do you add items to the array to the front?

Answer 42

variableNames.unshift('item', 'itemB')

Question 43

How would you extract the max number in a list of numbers using the spread operator? const numbers = [10, 20, 30, 40];

Answer 43

See the console.log

Question 44

What does Math.max do?

Answer 44

Produces the highest number in a list within an array

Question 45

What does Math.min do?

Answer 45

It selects the lowest number within an array.

Question 46

Can you use the .push() method to add more than one element to an array at the same time? Is the following example, valid? scores.push( 77, 76, 89);

Answer 46

Yes. You can use push() to add any number of elements to the end of an array.

Question 47

Please fill in the correct answer. Complete the code by using the property that returns the number of elements in the attendees array.

Answer 47

attendees.length

Question 48

Which array method adds an element to the end of an array?

Answer 48

.push()

Question 49

Which of the following places the contents of one array into another array?

Answer 49

The spread operator (...)

Question 50

Which array method returns the first element of an array and removes it from the array?

Answer 50

**.shift()** removes first item from beginning of the array

Question 51

Complete the code below to add the value of 23 the beginning of the ages array.

Answer 51

ages.unshift(23);

Question 52

What is the zero index values for the following array of students?

Answer 52

Order/Name 0 Lee 1 Jan 2 Mali 3 Sarah

Question 53

What happens when the loop counter reaches 4?

Answer 53

When it reaches 4, it breaks the loop as the array doesn’t have a 4th item.

Question 54

Why would you use a variable length counter?

Answer 54

students.length is superior coding because it adjusts to changes in the array better If student number changes, up/down, program is flexible enough to run.

Question 55

What function would you use to create items in a list?

Answer 55

function is createListItems

Question 56

What is arr?

Answer 56

Parameter

Question 57

What does the ${arr[i]}?

Answer 57

It returns values that matches i variable

Question 58

What's the role of return items;?

Answer 58

it’s key to calling function

Question 59

What does the document.querySelector section of code produce?

Answer 59

It puts all the songs in an ordered playlist

Question 60

What symbol do you use to keep conditions separate?

Answer 60

use the semi-colon ; to separate conditions

Question 61

Do you need a symbol after the closing curly brace }?

Answer 61

No, you don't need a ; after a } curly brace.

Question 62

What does the the .join array method do?

Answer 62

.join() method creates and returns a new string by concatenating all of the elements in an array, separated by commas or specified separator string. Joins list items in a variable by giving it a format consisting with spaces, dashes, or punctuation

Question 63

What does the array method .includes() do?

Answer 63

determines whether or not an item is found within an array by providing an answer as True or False for Yes and No respectively true or false true: found false: not found

Question 64

If an item is found within an array, what response does the .includes() array method provide?

Answer 64

True

Question 65

What happens if you use the array method .includes() for an item that's not found within an array, what response is provided in the JavaScript console?

Answer 65

False Not found in the array

Question 66

Is the .includes() array method case sensitive?

Answer 66

Yes It's case sensitive. The wrong case creates an error Stick to lowercase

Question 67

What does **.indexOf** array method do?

Answer 67

Checks if value is found within an array

Question 68

Using the .indexOf array method how does it use the zero index method?

Answer 68

-1 not found if it is found in the array

Question 69

What does a positive number mean in the context of the .indexOf array method mean?

Answer 69

Positive numbers means the item is found in the list of array items

Question 70

What does a negative number mean in the context of .indexOf()?

Answer 70

Negative number = not in the list of array items

Question 71

Use the array method that combines all of the elements inside the planets array into a single string. The final string should separate the array elements by a comma and space. Log the final string value to the console.

Answer 71

Logs the final string value to the console with the .join array method giving it a comma and space to bring the list items together with correct formatting

Question 72

Next, use the method that returns the position of 'Saturn' in the planets array. Log the return value to the console.

Answer 72

console.log(variableName.indexOf('Saturn'));

Question 73

How do you write an if/else statement to search an array based on a search? Just the if/else section

Answer 73

if (variableName.includes(search) { message= `Yes, we have ${search}`; } else { message = `Sorry, we don't have ${search}`;

Question 74

How do you explain the logic behind this program?

Answer 74

FIrst, establish a variable assigned to an array with the list of items. Second, create a variable that asks a prompt question Create a third variable for the reply to the question Fourth, create an if/else statement that searches the first variable using the second variable question to then produce yes/no messages if item is or isnt in stock

Question 75

What array method would you use to search the grocery list items to see if it is in stock?

Answer 75

.indexOf array method

Question 76