Intro to JavaScript

Question 1

What is console?

Answer 1

A keyword that refers to an object, a collection of data and actions.

Question 2

What is a keyword?

Answer 2

Words that are built into the JavaScript language so the computer will recognize them and treats them specifically.

Question 3

How to use .log()

Answer 3

console.log() - what is put in the parenthesis will get printed/logged in the console.

Question 4

What are the 7 fundamental data types?

Answer 4

Number, String, Boolean, Null, Undefined, Symbol, Object

Question 5

What is an undefined data type?

Answer 5

It represents the absence of a value though it has a different use than NULL

Question 6

What is a symbol data type?

Answer 6

Unique identifiers, useful in more complex coding.

Question 7

What is an object data type?

Answer 7

Collections of related data.

Question 8

Are number data types allowed decimals?

Answer 8

Yes

Question 9

What is a variable?

Answer 9

You can think of a variable as a container for a value.

Question 10

What are the few things you can do with variables?

Answer 10

1. Create a variable with a descriptive name
2. Store or update information stored in a variable
3. Reference or “get” information stored in a variable

Question 11

What does var do?

Answer 11

Keyword that creates, or declares, a new variable.

Question 12

What are rules of naming variables?

Answer 12

1. Variable names cannot start with numbers
2. Variable names are case sensitive
3. Variable names cannot be the same as keywords

Question 13

What does the let keyword allow for?

Answer 13

This keyword signals that the variable can be reassigned a different value.

Question 14

What value does a var have if we initiate it without a value?

Answer 14

Undefined

Question 15

What does the const keyword do?

Answer 15

Create a variable that cannot be reassigned. These must be assigned a variable when they are declared.

Question 16

What is a template literal?

Answer 16

A function(?) that lets you add variables into strings.
Must use ~ instead of '.

Question 17

Give an example of a template litera?

Answer 17

console.log(My name is ${variable})

Question 18

Example of an if statement

Answer 18

if (false) {

console.log(‘The code in this block will not run.’);

Question 19

What operator do you use to say “Is equal to”?

Answer 19

===

Question 20

What operator do you use to say “Is not equal to”?

Answer 20

!==

Question 21

What does the and operator look like?

Answer 21

&&

Question 22

What does the or operator look like?

Answer 22

||

Question 23

What does the not operator look like?

Answer 23

!

Question 24

Which values are falsy or evaluate to falsy?

Answer 24

0, Empty strings like “” or ‘’, null, undefined, Nan

Question 25

What is the syntax to a switch statement?

Answer 25

switch (groceryItem) { case 'tomato': console.log('Tomatoes are $0.49'); break;

Question 26

What is one way of declaring a function?

Answer 26

By using the keyword function followed by the name of the function. function your name() {}

Question 27

When does a function execute?

Answer 27

When the function is called. You need to type toe function followed by (). Example, function();

Question 28

What do parameters do in a function?

Answer 28

Allow functions to accept input(s) and perform a task using the input(s). They are placeholders for information that will be passed to the function when it is called.

Question 29

What is a default parameter?

Answer 29

Default parameters allow parameters to have a predetermined value in case there is no argument passed into the function or if the argument is undefined when called.

Question 30

What does a zero parameter FAT ARROW function look like?

Answer 30

const funcitonName = () => {};

Question 31

What does a one parameter FAT Arrow function look like?

Answer 31

const functionName = paramOne => {};

Question 32

What does a two parameter FAT ARROW function look like?

Answer 32

const functionName = (paramOne, paramTwo) => {};

Question 33

What does a function body compopsed of a single-line block look like?

Answer 33

const sumNumbers = number => number + number;

Question 34

What does a function body composed of a multiple lines of block look like?

Answer 34

``` const sumNumbers = number => { const sum = number + number; return sum; }; ```

Question 35

What does scope do?

Answer 35

Scope defines where variables can be accessed or referenced.

Question 36

What are blocks?

Answer 36

A block is the code found inside a set of curly braces {}. They help us group one or more statements together and serve as an important structural marker for our code.

Question 37

Where is a global scope declared?

Answer 37

Global scope variables are declared outside of blocks | This allows them to be accessed by any code in the program.

Question 38

What is block scope?

Answer 38

context within which variables that are accessible only within the block they are defined.

Question 39

What is Scope Pollution?

Answer 39

When you have too many global variables that exist in the global namespace. Or when we reuse variables across different scopes.

Question 40

What are local variables?

Answer 40

Variables that exist within block scope

Question 41

What is an array?

Answer 41

Javascript's way of making lists.

Question 42

What is the syntax for an array?

Answer 42

['content of array', 'content 2 of array', 'array can have numbers', 10]

Question 43

What is the content item inside an array called?

Answer 43

An element

Question 44

What is the name of the numbered position of each element?

Answer 44

Index

Question 45

What does the .length property let you know about an array?

Answer 45

It lets you know how many elements are in an array. it is used by adding .length to the end of an array/variable. variable.length

Question 46

What does the.push() method allow us to do?

Answer 46

It allows us to add items to the end of an array

Question 47

Example of the .push() method

Answer 47

const itemTracker = ['item 0'] itemTracker.push('item 3') console.log(itemTracker) // returns ['item 0', ' item 3']

Question 48

What does the .pop() method do?

Answer 48

The .pop() method removes the last item of an array.

Question 49

What does the .shift() method do?

Answer 49

It removes the first item from an array

Question 50

What does the .unshift() method do?

Answer 50

It takes an argument .unshift('argument') and adds it to the beginning of an array. Can take multiple arguments.

Question 51

What is a loop?

Answer 51

Programming tool that repeats a set of instructions until a specified condition, called a stopping condition, is reached.

Question 52

What are the 3 expressions contained in all for loops?

Answer 52

1. Initialization (what starts the loop) 2. stopping condition (condition that the iterator variable is evaluated against) 3. Iteration statement (used to update the iterator variable on each loop)

Question 53

Tell me what the syntax for a for loop should look like?

Answer 53

``` for (let i = 0; i < bobsFollowers.length; i++){ for (let j = 0; j < tinasFollowers.length; j++){ if(bobsFollowers[i] === tinasFollowers[j]){ mutualFollowers.push(bobsFollowers[i]) } } } ```

Question 54

When to use a for loop?

Answer 54

We use a for loop when we know how many times the loop should run

Question 55

What is a higher-order function?

Answer 55

Higher-Order-Functions are functions that accept other functions as arguments and/or return functions as output.

Question 56

What are callback functions?

Answer 56

Functions that get passed in as parameters and invoked. This is because they get called during the execution of the higher-order function

Question 57

What does the this keyword reference?

Answer 57

It references the CALLING object which provides access to the CALLING object's properties

Question 58

What type of formatting should you avoid when using the THIS keyword

Answer 58

BIG ARROW formatting - forces the function to bind in the GLOBAL environment rather than the CALLING object.

Question 59

What are GETTERS?

Answer 59

Getters are methods that get and return the internal properties of an object.

Question 60

What are SETTERS?

Answer 60

Methods that reassign values of existing properties within an object.

Question 61

What are factory functions?

Answer 61

a function that returns an object and can be reused to make multiple object instances. They can also have parameters allowing us to customize the object that gets returned.

Question 62

What are classes in JS?

Answer 62

Classes are a tool that developers use to quickly produce similar objects.

Question 63

What is an instance in JS?

Answer 63

An instance is an object that contains the property names and methods of a class but with unique property values.

Question 64

What does the "Extends" keyword do in a class?

Answer 64

Makes the methods of a class available inside the new class.

Question 65

What does the "super" keyword do in a constructor argument?

Answer 65

IT helps pass the argument past the first class and onto the parent class. Note: You must always call the super method before you can use the this keyword.