JavaScript

Question 1

What is the purpose of variables?

Answer 1

Store information for the script to its job.

Question 2

How do you declare a variable?

Answer 2

First use the variable keyword, then the variable name.

Question 3

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

Answer 3

After the variable name use the equal sign or assignment operator then the variable value.

Question 4

What characters are allowed in variable names?

Answer 4

letters, underscore, dollar sign, numbers.

Question 5

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

Answer 5

The language keywords, variables, function names, and any other identifiers must always be typed with a consistent capitalization of letters.

Question 6

What is the purpose of a string?

Answer 6

Working with any kind of text. Represent and manipulate a sequence of characters.

Question 7

What is the purpose of a number?

Answer 7

Working with numeric data.

Question 8

What is the purpose of a boolean?

Answer 8

Create true or false statements. Determine which part of a script should run.

Question 9

What does the = operator mean in JavaScript?

Answer 9

Is an assignment operator. Is used to give the value to a variable.

Question 10

How do you update the value of a variable?

Answer 10

Just use the variable name, the equals sign and the new value.

Question 11

What is the difference between null and undefined?

Answer 11

Undefinided is a variable has been declared but has not been assigned a value. Null is an assignment value. It can be assigned to a variable as a representation of no value.

Question 12

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

Answer 12

Is good to avoid confusions between similar values.

Question 13

Give five examples of JavaScript primitives.

Answer 13

String, number, boolean, null, undefined.

Question 14

What data type is returned by an arithmetic operation?

Answer 14

Numerical value.

Question 15

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

Answer 15

The addition operator ( + ) produces the sum of numeric operands or string concatenation

Question 16

What data type is returned by comparing two values (<, >, ===, etc)?

Answer 16

A boolean value (true or false).

Question 17

What does the += “plus-equals” operator do?

Answer 17

The addition assignment operator (+=) adds the value of the right operand to a variable and assigns the result to the variable.

Question 18

What is string concatenation?

Answer 18

Join two or more strings values into one value.

Question 19

What are object properties?

Answer 19

An association between a name (or key) and a value

Question 20

Describe object literal notation.

Answer 20

Value pairs, with a colon separating the keys and values, and a comma after every key:value pair, except for the last one

Question 21

How do you remove a property from an object?

Answer 21

Using the delete operator.

Question 22

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

Answer 22

With a dot and with brackets.

Question 23

What are objects used for?

Answer 23

For store data as properties (key-value pairs).

Question 24

What are arrays used for?

Answer 24

Used to store values that are related to each other.

Question 25

Describe array literal notation.

Answer 25

a list of zero or more expressions, each of which represents an array element, enclosed in square brackets ( [] )

Question 26

What number represents the first index of an array?

Answer 26

zero.

Question 27

What is the length property of an array?

Answer 27

size of the array or the total number of elements present in the array.

Question 28

How do you calculate the last index of an array?

Answer 28

Get the last element of ArrayList with use of get(index) method by passing index = size – 1.

Question 29

How are arrays different from “plain” objects?

Answer 29

Arrays are used when we store multiple values ​​of a single variable, while an object can contain multiple variables or properties with their values.

Question 30

What is a function in JavaScript?

Answer 30

A JavaScript function is a block of code designed to perform a particular task.

Question 31

Describe the parts of a function definition.

Answer 31

1. • Function keyword
2. • Optional name.
3. • Parameters separated by a comma.
4. • Opening curly brace { for the code block.
5. • Optional return.
6. -Closing curly brace} for the code block

Question 32

Describe the parts of a function call.

Answer 32

The function’s name. A comma separated the arguments surrounded by parentheses.

Question 33

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

Answer 33

Define a function doesn’t cause the code block run because is just an object. Call an object does the code block run.

Question 34

What is the difference between a parameter and an argument?

Answer 34

parameters are the name within the function definition.

Arguments are the values passed in when the function is called.

Question 35

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

Answer 35

1. • Causes the function to produce a value we can use in our program
2. • Used to stop the function.

Question 36

Why are function parameters useful?

Answer 36

They received the arguments that are passed when the function is called.

Question 37

What are the four components of “the Cascade”.

Answer 37

1. • Source order
2. • Inheritance
3. • Specificity
4. • !important

Question 38

Why do we log things to the console?

Answer 38

to verify that what we are doing is correct

Question 39

What is a method?

Answer 39

Is statement or code block that performs a specific task.

Question 40

How is a method different from any other function?

Answer 40

Method is function that belongs to an object while function not.

Question 41

How do you remove the last element from an array?

Answer 41

With pop method

Question 42

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

Answer 42

Math.floor method

Question 43

How do you generate a random number?

Answer 43

Random method

Question 44

How do you delete an element from an array?

Answer 44

splice method

Question 45

How do you append an element to an array?

Answer 45

Push method

Question 46

How do you break a string up into an array?

Answer 46

split method

Question 47

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

Answer 47

No, we can console.log the original variable

Question 48

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

Answer 48

MDN

Question 49

Give 6 examples of comparison operators.

Answer 49

strictly equal(===), not equal to (!=), not strict equal to(!==), greater than (>), less than(<), greater or equal than (>=), less or equal than (<=).

Question 50

What data type do comparison expressions evaluate to?

Answer 50

Boolean values

Question 51

Is else required in order to use an if statement?

Answer 51

No

Question 52

What are the three logical operators?

Answer 52

logical and(&&), logical or (| |), logical not (!)

Question 53

Syntax of an if statement

Answer 53

if keyword, condition, opening curly brace, code to execute if value is true, closing curly bracket

Question 54

What is the purpose of a loop?

Answer 54

repeat the same, or similar, code a number of times. Simplify work.

Question 55

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

Answer 55

tested each time the loop repeats.

Question 56

What does “iteration” mean in the context of loops?

Answer 56

sequence of instructions that is continually repeated.

Question 57

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

Answer 57

An expression evaluated before each pass through the loop.

Question 58

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

Answer 58

before the execution of the first loop.

Question 59

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

Answer 59

each time before the loop runs.

Question 60

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

Answer 60

This expression is executed after each iteration of the loop

Question 61

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

Answer 61

Break keyword

Question 62

What does the ++ increment operator do?

Answer 62

increases the value of a variable by 1

Question 63

How do you iterate through the keys of an object?

Answer 63

With for..in loops.

Question 64

Why do we log things to the console?

Answer 64

Test if what we did works before to print the final result to the user.

Question 65

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

Answer 65

HTML document

Question 66

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

Answer 66

Represent each object that conform the structure and content of a document on the web.

Question 67

What is a DOM Tree?

Answer 67

Structure of nested nodes.

Question 68

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

Answer 68

querySelector() and getElementById()

Question 69

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

Answer 69

getElementsByClassName()

Question 70

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

Answer 70

If you want to work with that element more than once

Question 71

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

Answer 71

console.dir()

Question 72

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

Answer 72

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

Question 73

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

Answer 73

Takes a string that contains css selector describing the HTML element you want to work with. Returns only the first of the matching elements

Question 74

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

Answer 74

Takes a css selector and returns all of those that match.

Question 75

What is a model?

Answer 75

a representation of something else

Question 76

Why do we log things to the console?

Answer 76

To see how our code is working

Question 77

What is the purpose of events and event handling?

Answer 77

Allows the page to be interactive

Question 78

What method of element objects lets you set up a function to be called when a specific type of event occurs?

Answer 78

.addEventListener()

Question 79

What is a callback function?

Answer 79

A call back function is a function that is passed into another function as an argument.

Question 80

What object is passed into an event listener callback when the event fires?

Answer 80

Event object

Question 81

What is the event.target? If you weren’t sure, how would you check? Where could you get more information about it?

Answer 81

Where interactions occurred. You can log it or with debugger. MDN

Question 82

What is the difference between these two snippets of code?

element. addEventListener(‘click’, handleClick)
element. addEventListener(‘click’, handleClick())

Answer 82

The first one runs the eventlistener when the event is fired. The last one indicates that the event listener should run as the page loads

Question 83

What is the className property of element objects?

Answer 83

A string containing the value of a class attribute on that element.

Question 84

How do you update the CSS class attribute of an element using JavaScript?

Answer 84

With classname property: .className

Question 85

What is the textContent property of element objects?

Answer 85

Is a string containing the value of the text content of an element

Question 86

How do you update the text within an element using JavaScript?

Answer 86

By using textContent property

Question 87

Is the event parameter of an event listener callback always useful?

Answer 87

Not always

Question 88

Would this assignment be simpler or more complicated if we didn’t use a variable to keep track of the number of clicks?

Answer 88

More complicated

Question 89

Why is storing information about a program in variables better than only storing it in the DOM?

Answer 89

Easier access for later use

Question 90

Give four examples of CSS transform functions.

Answer 90

Matrix, translate, scale, rotate, skew.

Question 91

What does the transform property do?

Answer 91

Lets you rotate, scale, skew, or translate an element. It modifies the coordinate space of the CSS visual formatting model.

Question 92

What event is fired when a user places their cursor in a form control?

Answer 92

Focus control

Question 93

What event is fired when a user’s cursor leaves a form control?

Answer 93

blur event

Question 94

What event is fired as a user changes the value of a form control?

Answer 94

input event

Question 95

What event is fired when a user clicks the “submit” button within a ?

Answer 95

submit event

Question 96

What does the event.preventDefault() method do?

Answer 96

Prevents the default function of an element

Question 97

What does submitting a form without event.preventDefault() do?

Answer 97

Reloads the page

Question 98

What property of a form element object contains all of the form’s controls.

Answer 98

elements property

Question 99

What property of a form control object gets and sets its value?

Answer 99

value property

Question 100

What is one risk of writing a lot of code without checking to see if it works so far?

Answer 100

You don’t know if or where things are failing.

Question 101

What is an advantage of having your console open when writing a JavaScript program?

Answer 101

Ability to check if your code is working.

Question 102

Does the document.createElement() method insert a new element into the page?

Answer 102

No, it only creates an element, but does not insert it into the page. .

Question 103

How do you add an element as a child to another element?

Answer 103

How do you add an element as a child to another element?

Question 104

What do you pass as the arguments to the element.setAttribute() method?

Answer 104

two string representing an attribute and its value

Question 105

What steps do you need to take in order to insert a new element into the page?

Answer 105

create the element, give the element some content, and insert the element into the page.

Question 106

What is the textContent property of an element object for?

Answer 106

setting or getting text of an element

Question 107

Name two ways to set the class attribute of a DOM element.

Answer 107

.setAttribute and .className

Question 108

What are two advantages of defining a function to do create something (like the work of creating a DOM tree)?

Answer 108

• • automate repetitive work

- - can be reusedcan change it anytime

Question 109

What is the event.target?

Answer 109

The element most directly interacted with by an event. The target of the event (most specific element interacted with)

Question 110

Why is it possible to listen for events on one element that actually happen its descendent elements?

Answer 110

event bubbling

Question 111

What DOM element property tells you what type of element it is?

Answer 111

tagName

Question 112

What does the element.closest() method take as its argument and what does it return?

Answer 112

A selector containing a selector list, and it returns the element which is the closest ancestor of the element.

Question 113

How can you remove an element from the DOM?

Answer 113

.remove()

Question 114

If you wanted to insert new clickable DOM elements into the page using JavaScript, how could you avoid adding an event listener to every new element individually?

Answer 114

Adding event listener to the parent that will contain the new item with bubbling event

Question 115

What is the event.target?

Answer 115

The object of that event is ocurring

Question 116

What is the affect of setting an element to display: none?

Answer 116

Turns off the display of an element and acts as if it was not there.

Question 117

What does the element.matches() method take as an argument and what does it return?

Answer 117

It takes a selector in the form of a string and returns a boolean.

Question 118

How can you retrieve the value of an element’s attribute?

Answer 118

.getAttribute() method

Question 119

At what steps of the solution would it be helpful to log things to the console?

Answer 119

Every step

Question 120

If you were to add another tab and view to your HTML, but you didn’t use event delegation, how would your JavaScript code be written instead?

Answer 120

you would have to add an event listener for each tab and view

Question 121

If you didn’t use a loop to conditionally show or hide the views in the page, how would your JavaScript code be written instead?

Answer 121

many if/else statements.
t would have more code to check every tab.
conditionals for for each one

Question 122

What is JSON?

Answer 122

JavaScript Object Notation and it is lightweight data-interchange format.

Question 123

What are serialization and deserialization?

Answer 123

serialization: converting a native object to a string so it can be transmitted across the network or it can be stored
deserialization: Converting a string to a native object

Question 124

Why are serialization and deserialization useful?

Answer 124

Sending information over a network.
for data exchange and storing data without having to rely on it storing as a reference in your computer

it allows you to save the state of an object and convert it to 1s and 0s so it can be transferred over networks and then it can be translated back into an object through deserialization

Question 125

How do you serialize a data structure into a JSON string using JavaScript?

Answer 125

JSON.stringify( ) method

Question 126

How do you deserialize a JSON string into a data structure using JavaScript?

Answer 126

JSON.parse( ) method

Question 127

How do you store data in localStorage?

Answer 127

call the setItem method of the localStorage object.

Question 128

How do you retrieve data from localStorage?

Answer 128

call the getItem method of the localStorage object.

Question 129

What data type can localStorage save in the browser?

Answer 129

key/value pairs in the form of strings.

Question 130

When does the ‘beforeunload’ event fire on the window object?

Answer 130

just before the program closes, while the content is still visible.
The beforeunload event is fired when the page is about to be unloaded.
Before everything is dumped out of the memory from the browser.

Question 131

What is a method?

Answer 131

A function which is a property of an object.

Question 132

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

Answer 132

A method definition has the keyword function and the code block following it. A method call only has the argument inside of the method.

Question 133

Describe method definition syntax (structure).

Answer 133

property name followed by the function keyword and its parameters. And then a code block that has the necessary code.

Question 134

Describe method call syntax (structure).

Answer 134

object followed by a period and the property after. And then parenthesis to hold the given arguments for that method call.
object.methodName()
obj, method name, arguments.

Question 135

How is a method different from any other function?

Answer 135

A method is a property thats defined within that object, while a normal function is a method of the global scope (window).

Question 136

What is the defining characteristic of Object-Oriented Programming?

Answer 136

Objects can contain both data (as properties) and behavior (as methods).

Question 137

What are the four “principles” of Object-Oriented Programming?

Answer 137

Abstraction
Encapsulation
Inheritance
Polymorphism

Question 138

What is “abstraction”?

Answer 138

Being able to work with (possibly) complex things in simple ways.

Question 139

What does API stand for?

Answer 139

Application Programming Interface

Question 140

What is the purpose of an API?

Answer 140

To allow a programmer a way to interact with a system in a simplified way.

Question 141

What is this in JavaScript?

Answer 141

An implicit parameter that allows us to see the object that ‘this’ is being invoked upon.

Question 142

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

Answer 142

It is available in a functions code block even though it was never included in the function’s parameter list or declared with var.

Question 143

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

Answer 143

When function is called

The value of this is determined when the function is called, not when it is defined.

Question 144

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 144

Mario

Question 145

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

Answer 145

The greet method of the character object is call. This method includes a string that is concatenated with this.FirstName.
It would return: ‘It’s-a-me, Mario!’
Because character is the object which contains the method ‘greet’, which refers to the firstName property of character in its codeblock

Question 146

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

Answer 146

undefined.

this is attached to hello when it is called with hello. hello does not have a firstName property. this is attached to whoever is calling the function.

It returns the message + undefined because this.firstName isn’t defined within the variable hello. This keyword is now attached to hello rather than the firstName property of the character object.

Question 147

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

Answer 147

you can’t tell until the method or function is called.
you can tell what [this] will be because it is attached to an object. so [this] is referring the object that it is contained in.

Question 148

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

Answer 148

look at the object left of the dot when the function or method is being called

Question 149

What kind of inheritance does the JavaScript programming language use?

Answer 149

prototype based

Question 150

What is a prototype in JavaScript?

Answer 150

An object that contains properties and (predominantly) methods that can be used by other objects.

Question 151

How is it possible to call methods on strings, arrays, and numbers even though those methods don’t actually exist on strings, arrays, and numbers?

Answer 151

Those methods are defined on a “prototype” object and arrays simply borrow those methods when they’re needed.

Question 152

If an object does not have it’s own property or method by a given key, where does JavaScript look for it?

Answer 152

The prototype chain

Question 153

What does the new operator do?

Answer 153

Creates a new instance of an object.

Creates a blank object
Sets the constrcutor of new object to other object
Passes new object as this
Returns this if the function does not return an object

Question 154

What property of JavaScript functions can store shared behavior for instances created with new?

Answer 154

Prototype

Question 155

What does the instanceof operator do?

Answer 155

Check if the object is inheriting from the specified object.
The instanceof operator tests to see if the prototype property of a constructor appears anywhere in the prototype chain of an object. The return value is a boolean value.
tests the presence of constructor.prototype in object’s prototype chain

Question 156

Besides adding an event listener callback function to an element or the document, what is one way to delay the execution of a JavaScript function until some point in the future?

Answer 156

settimeout() method

Question 157

What is a “callback” function?

Answer 157

is a function passed into another function as an argument, which is then invoked inside the outer function to complete some kind of routine or action.

Question 158

How can you set up a function to be called repeatedly without using a loop?

Answer 158

setInterval() method.

Question 159

What is the default time delay if you omit the delay parameter from setTimeout() or setInterval()?

Answer 159

The default time delay is 0, which executes immediately. or more accurately, the next event cycle.

Question 160

What do setTimeout() and setInterval() return?

Answer 160

The returned timeoutID is a positive integer value which identifies the timer created by the call to setTimeout();

The returned intervalID is a numeric, non-zero value which identifies the timer created by the call to setInterval()

Question 161

What is AJAX?

Answer 161

A technique for loading data into part of a page without having to refresh the entire page. Data is often sent in JSON format.
increasing the user experience and better performance.

Question 162

What does the AJAX acronym stand for?

Answer 162

Asynchronous JavaScript and XML

Question 163

Which object is built into the browser for making HTTP requests in JavaScript?

Answer 163

XMLHttpRequest()

Question 164

What event is fired by XMLHttpRequest objects when they are finished loading the data from the server?

Answer 164

load event

Question 165

An XMLHttpRequest object has an addEventListener() method just like DOM elements. How is it possible that they both share this functionality?

Answer 165

there is an EventTarget prototype object that is the prototype of the XMLHttpRequest that has the addEventListener method

both DOM elements and XMLHttpRequest objects inherit the method from the same prototype (EventTarget) that does have that method.

Both inherit the EventTarget method from the DOM interface
prototype chain
Both inherit the EventTarget method from the DOM interface

Question 166

What is a code block? What are some examples of a code block?

Answer 166

A code block is a set of code that is grouped together, usually by using {}. Functions, loops, and conditionals have code blocks. - if/else, for, do while, while, try, catch, etc.

a chunk of code that will do a specific task when appropriate (when the function is called or a conditional is met/true)

Question 167

What does block scope mean?

Answer 167

the variables exist only within the corresponding block; variables are not visible outside the block

as opposed to function scoped.
inside the code block
- things that happen inside the curl braces.

block scope refers to the area within code block

variables exist only within the corresponding bloc

Question 168

What is the scope of a variable declared with const or let?

Answer 168

block-scoped

Question 169

What is the difference between let and const?

Answer 169

The difference is that let is mutable while const is a read-only reference.

const keyword creates block-scoped variables whose values can’t be reassigned

let - mutable, const- immutable

Question 170

Why is it possible to .push() a new value into a const variable that points to an Array?

Answer 170

• because we are not reassigning a block-scope, we’re just modifying the array held by the const variable
• const’s values can change/be mutated, but it cannot be reassigned to a dif block-scope value

Question 171

How should you decide on which type of declaration to use?

Answer 171

If a variable is not going to need changing, const should be used. If the variable may need its value updated, let is the right way to declare.

is the whole variable being reassigned (let), or are just the values inside the variable changing (const)

arrays & objects, always CONST

Question 172

What is the syntax for writing a template literal?

Answer 172

wrap the string in backticks

any expressions or variables go inside curly braces with a dollar sign before

Question 173

What is “string interpolation”?

Answer 173

ability to substitute part of the string for the values of variables or expressions.

String interpolation is the process of evaluating a string that contains one or more placeholders(variables), which will be replaced by their appropriate values when the string is evaluated.

To replace variables and expressions with their values within a string.

Question 174

What is destructuring, conceptually?

Answer 174

Taking properties and values from an object and assigning their values to independent variable.

• a way to assign the properties of an object to individual variables
• to get values from an object.
  way of extracting multiple values from data stored in (possibly nested) objects and Arrays.

Question 175

What is the syntax for Object destructuring?

Answer 175

const {names you want to assign to your variables} = object

Declare a variable followed by the curly brace. Property names are assigned to variables with the colon sign in between. Followed by a closing curly brace. and that whole code block is assigned to a variable name.

const/let keyword,
curly braces,
variable names within curly brace,
assignment operator,
variable

Question 176

What is the syntax for Array destructuring?

Answer 176

const/let keyword,
brackets,
variable names,
assignment operator,
variable

Question 177

How can you tell the difference between destructuring and creating Object/Array literals?

Answer 177

creating, on the right
destructuring, on the left

destructuring, check for variable name at the end

or if there is no variable name following const/let

Question 178

What is the syntax for defining an arrow function?

Answer 178

parameter list, arrow, codeblock

let funcName = (parameter) => { return expression; };

one param - param => expression (for anonymous)
multiple params - (param1, param2) => expression, requires parantheses
multiple statements - require body brackets and return

(param1, param2)=>{ return;}:
param=> exp;
()=>exp

Question 179

When an arrow function’s body is left without curly braces, what changes in its functionality?

Answer 179

No return keyword is needed. The keyword return is implied for the body. If there are multiple expressions to compute, then the return won’t occur.

Function body is

Question 180

How is the value of this determined within an arrow function?

Answer 180

The value of this is determined at the time the arrow function is defined.

Question 181

What is a CLI?

Answer 181

command line interface. processes commands to a computer program in the form of lines of text

Question 182

What is a GUI?

Answer 182

graphical user interface. is a form of user interface that allows users to interact with electronic devices through graphical icons and audio indicator such as primary notation, instead of text-based user interfaces, typed command labels or text navigation.

is a system of interactive visual components for computer software. A GUI displays objects that convey information, and represent actions that can be taken by the user. The objects change color, size, or visibility when the user interacts with them.

Question 183

Give at least one use case for each of the commands listed in this exercise.
man
cat
ls
pwd
echo
touch
mkdir
mv
rm
cp

Answer 183

man- interface to online reference manuals (use when there’s a command you don’t know much about)

cat- concatenate files and print on the standard output (use when you want to see contents of file or even combine files together in a new file)

ls- list directory contents (when you want to see what is inside the current directory)
(-a do not ignore entries that start with .
- F append indicator to entries)

pwd- print name of current/working directory ( when you want to know which directory you are in currently)

echo- display a line of text (when you want to display text and possibly put that text into a file)

touch- create new files

mkdir- make directories
(-p makes parent directories as needed)

mv- rename files/directories

rm- delete files
(-r removes directories and all their contents
-f ignore nonexistent files and arguments, never prompt)

cp- copy files and directories
(-r copy directories recursively)

Question 184

What are the three virtues of a great programmer?

Answer 184

Laziness, Impatience, Hubris

Question 185

What is Array.prototype.filter useful for?

Answer 185

It is useful for creating a new array when you only want to grab specific values from an existing array that meet a specific condition.

Question 186

What is Array.prototype.map useful for?

Answer 186

when you want to run a function on every index in the array and return the same amount of values as the input array

creating a new array containing the values resulting from calling a provided callback function on each value of an array

Question 187

What is Array.prototype.reduce useful for?

Answer 187

for reducing an array to a single value using a provided callback function

When you want to run a function on every index in the array and return a single value