SENIOR SIDE

Question 1

ES6-CONST-LET

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

Answer 1

a code block is anything within curly braces.

i.e. function code block, if statements, etc.

Question 2

ES6-CONST-LET

What does block scope mean?

Answer 2

it means that variable declared within the code block are only for that block, i.e. local vs global variables

Question 3

ES6-CONST-LET

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

Answer 3

block scope

Question 4

ES6-CONST-LET

What is the difference between let and const?

Answer 4

VAR Yes Yes Function Scope Yes
LET Yes No Block Scope No
CONST No No Block Scope No

Question 5

ES6-CONST-LET

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

Answer 5

When you’re adding to an array or object you’re not re-assigning or re-declaring the constant, it’s already declared and assigned, you’re just adding to the “list” that the constant points to.

ex: we are not changing the typeof in the variable

Question 6

ES6-CONST-LET

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

Answer 6

whether or not you ever want that variable to be redeclared or reassigned???

Question 7

ES6-TEMPLATE-LITERALS

What is the syntax for writing a template literal?

Answer 7

` some text and ${some variable or property}`

Question 8

ES6-TEMPLATE-LITERALS

What is “string interpolation”?

Answer 8

string interpolation is the process of evaluating a string literal containing one or more placeholders ${someVariable}, yielding a result in which the placeholders are replaced with their corresponding values.

Question 9

ES6-DESTRUCTURING

What is destructuring, conceptually?

Answer 9

it is breaking down an object or array and assigning key/value pairs to a variable/value pair

Question 10

ES6-DESTRUCTURING

What is the syntax for Object destructuring?

Answer 10

name = {
firstName: ‘Andy’,
lastName: ‘Chen’
}

const { firstName, lastName } = name
- this creates a variable named firstName with value of name.firstName and variable named lastName with a value of name.lastName

const { myName: firstName } = name
- this creates a variable named myName with value of name.firstName

Question 11

ES6-DESTRUCTURING

What is the syntax for Array destructuring?

Answer 11

const someArray = [0 , 1, 2, 3, 4]

const [number1, number2, number3] = someArray

or to get the last ones after number3 then
const [ , , , number4] = someArray

Question 12

ES6-DESTRUCTURING

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

Answer 12

braces on the right side of the equal sign are creating

braces on left-hand side and that’s destructuring

Question 13

ES6-ARROW-FUNCTIONS

What is the syntax for defining an arrow function?

Answer 13

const functionName = parameter => expression

or const functionName = (param1, param2) => param1 + param2

or const functionName = (param1, param2) => ( {param1:param2} )

Question 14

ES6-ARROW-FUNCTIONS

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

Answer 14

it has an implicit return

Question 15

ES6-ARROW-FUNCTIONS

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

Answer 15

arrow functions have a lexical scope (using global variables) so the value of ‘this’ is determined by the surrounding scope.

i.e. either window if it’s a global scope or local variable if arrow function is wrapped in a regular function

tim : arrow function = ‘this’ is defined at definition time
regular function = ‘this’ is defined at call time

Question 16

COMMAND-LINE-BASICS

What is a CLI?

Answer 16

command line interface

Question 17

COMMAND-LINE-BASICS

What is a GUI?

Answer 17

Graphical user interface

Question 18

COMMAND-LINE-BASICS

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 18

man = ultimate guide
cat = combine files
ls = check file directories
pwd = print current working directory
echo = print to terminal, like a console.log
touch = create a new file
mkdir = make directories / files
mv = move and renames file
rm = remove a file
cp = copy a file

Question 19

COMMAND-LINE-BASICS

What are the three virtues of a great programmer?

Answer 19

laziness, impatience, and hubris???

Question 20

NODE-INTRO

What is Node.js?

Answer 20

Node.js is a javascript runtime. A program that allows JavaScript to be run outside of a web browser.

Question 21

NODE-INTRO

What can Node.js be used for?

Answer 21

non-blocking, event driven servers

Question 22

NODE-INTRO

What is a REPL?

Answer 22

read-eval-print loop, interactive top level or language shell

Question 23

NODE-INTRO

When was Node.js created?

Answer 23

2009

Question 24

NODE-INTRO

What back end languages have you heard of?

Answer 24

Python, MySQL, Node.js

Question 25

NODE-PROCESS-ARGV What is the process object in a Node.js program?

Answer 25

It is an essential component in the Node.js ecosystem as it provides various information sets about the runtime of a program.

Question 26

NODE-PROCESS-ARGV How do you access the process object in a Node.js program?

Answer 26

``` const process = require('process'); or just using process since it's global ```

Question 27

NODE-PROCESS-ARGV What is the data type of process.argv in Node.js?

Answer 27

, an array of strings

Question 28

NODE-MODULE-SYSTEM What is a JavaScript module?

Answer 28

a JavaScript file containing related code

Question 29

NODE-MODULE-SYSTEM What values are passed into a Node.js module's local scope?

Answer 29

exports, require, module, __filename, __dirname ``` ex: (function (exports, require, module, __filename, __dirname) { // your code is here }); ```

Question 30

NODE-MODULE-SYSTEM Give two examples of truly global variables in a Node.js program.

Answer 30

setInterval, setTimeOut

Question 31

NODE-REQUIRE What is the purpose of module.exports in a Node.js module?

Answer 31

to export functions to another node.js module

Question 32

NODE-REQUIRE How do you import functionality into a Node.js module from another Node.js module?

Answer 32

const someVariable = require('./someFileName');

Question 33

THE-EVENT-LOOP What is the JavaScript Event Loop?

Answer 33

An event loop is something that pulls stuff out of the queue and places it onto the function execution stack whenever the function stack becomes empty.

Question 34

THE-EVENT-LOOP What is different between "blocking" and "non-blocking" with respect to how code is executed?

Answer 34

blocking = synchronous, won't allow the computer to do anything else until the code block is completely run through non-blocking = asynchronous can run other things while waiting

Question 35

NODE-FS-READFILE What is a directory?

Answer 35

it is a path to what people call a folder

Question 36

NODE-FS-READFILE What is a relative file path?

Answer 36

it is the actual file path to go from one directory to another

Question 37

NODE-FS-READFILE What is an absolute file path?

Answer 37

a file path from the root

Question 38

NODE-FS-READFILE What module does Node.js include for manipulating the file system?

Answer 38

fs module

Question 39

NODE-FS-WRITEFILE What method is available in the Node.js fs module for writing data to a file?

Answer 39

writeFile method

Question 40

NODE-FS-WRITEFILE Are file operations using the fs module synchronous or asynchronous?

Answer 40

asynchronous

Question 41

HTTP-MESSAGES-RECAP What is a client?

Answer 41

a device that request services

Question 42

HTTP-MESSAGES-RECAP What is a server?

Answer 42

something that responds to client requests

Question 43

HTTP-MESSAGES-RECAP Which HTTP method does a browser issue to a web server when you visit a URL?

Answer 43

GET

Question 44

HTTP-MESSAGES-RECAP What is on the first line of an HTTP request message?

Answer 44

start line (3 items) - http method (GET, PUT or POST) - URL - HTTP version ( HTTP/1.1)

Question 45

HTTP-MESSAGES-RECAP What is on the first line of an HTTP response message?

Answer 45

protocol version, status code, status text

Question 46

HTTP-MESSAGES-RECAP What are HTTP headers?

Answer 46

meta data formatted as key:value pairs

Question 47

HTTP-MESSAGES-RECAP Is a body required for a valid HTTP message?

Answer 47

no

Question 48

NPM-INTRO What is NPM?

Answer 48

stands for Node Package Manager - largest JS database of free code, used to share and download code - website, CLI, and registry

Question 49

NPM-INTRO What is a package?

Answer 49

package.json and directory with 1 or more files in it

Question 50

NPM-INTRO How can you create a package.json with npm?

Answer 50

npm init --yes

Question 51

NPM-INTRO What is a dependency and how to you add one to a package?

Answer 51

something that the package will need to run and | to download it use npm install on command line

Question 52

NPM-INTRO What happens when you add a dependency to a package with npm?

Answer 52

- dependencies object will be updated | - adds the node list to the package

Question 53

EXPRESS-INTRO How do you add express to your package dependencies?

Answer 53

npm install express

Question 54

EXPRESS-INTRO What Express application method starts the server and binds it to a network PORT?

Answer 54

listen method | - Binds and listens for connections on the specified host and port

Question 55

EXPRESS-HELLO-WORLD How do you mount a middleware with an Express application?

Answer 55

use the 'use' method on an express object | i.e. app.use( )

Question 56

EXPRESS-HELLO-WORLD Which objects does an Express application pass to your middleware to manage the request/response lifecycle of the server?

Answer 56

req for request and res for respond

Question 57

EXPRESS-GET-JSON What is the appropriate Content-Type header for HTTP messages that contain JSON in their bodies?

Answer 57

application/json

Question 58

EXPRESS-POST-JSON What does the express.json() middleware do and when would you need it?

Answer 58

parses incoming json body and need it when parsing incoming json bodies

Question 59

EXPRESS-DELETE What is the significance of an HTTP request's method?

Answer 59

tells the server if you're getting or posting

Question 60

POSTGRES-INTRO What is PostgreSQL and what are some alternative relational databases?

Answer 60

PostgreSQL is a relational database management system, mysql, SQL server by Microsoft, and Oracle by Oracle Corporation

Question 61

POSTGRES-INTRO What are some advantages of learning a relational database?

Answer 61

RDBMS VS non relational good at securing data and making complex queries vs non relational is better at storing more massive data they're everywhere, if you learn one, you basically know them all

Question 62

POSTGRES-INTRO What is one way to see if PostgreSQL is running?

Answer 62

sudo service postgresql status

Question 63

POSTGRES-DATABASE What is a database schema?

Answer 63

a collection of related tables

Question 64

POSTGRES-DATABASE What is a table?

Answer 64

list of rows with related attributes

Question 65

POSTGRES-DATABASE What is a row?

Answer 65

a set of attributes (columns)

Question 66

SQL-SELECT What is SQL and how is it different from languages like JavaScript?

Answer 66

SQLstands for Structured Query Language and it's different from JavaScript because it's a declarative langauge. SQL is like HTML and CSS where you describe the results and the programs renders the results.

Question 67

SQL-SELECT How do you retrieve specific columns from a database table?

Answer 67

SELECT "thisColumn", "thatColumn" | FROM thisTable;

Question 68

SQL-SELECT How do you filter rows based on some specific criteria?

Answer 68

SELECT "thisColumn", "thatColumn" FROM thisTable WHERE "thisColumn" > 1;

Question 69

SQL-SELECT What are the benefits of formatting your SQL?

Answer 69

looks cleaner and easier to read

Question 70

SQL-SELECT What are four comparison operators that can be used in a where clause?

Answer 70

<, >, =, !=

Question 71

SQL-SELECT How do you limit the number of rows returned in a result set?

Answer 71

at the very bottom LIMIT clause; SELECT "thisColumn", "thatColumn" FROM thisTable WHERE "thisColumn" > 1 LIMIT 5;

Question 72

SQL-SELECT How do you retrieve all columns from a database table?

Answer 72

SELECT * | FROM thisTable;

Question 73

SQL-SELECT How do you control the sort order of a result set?

Answer 73

order by clause can use desc or ascending is default

Question 74

SQL-INSERT How do you add a row to a SQL table?

Answer 74

insert into "table" ("col1", "col2") | values ('hello', 'world');

Question 75

SQL-INSERT What is a tuple?

Answer 75

a list of values

Question 76

SQL-INSERT How do you add multiple rows to a SQL table at once?

Answer 76

insert into "table" ("col1", "col2") values ('hello', 'world'), ('something', 'else');

Question 77

SQL-INSERT How do you get back the row being inserted into a table without a separate select statement?

Answer 77

insert into "table" ("col1", "col2") values ('hello', 'world'), ('something', 'else') returning *; <--- the returning clause with * to return all.

Question 78

SQL-UPDATE How do you update rows in a database table?

Answer 78

update "thisTable" set "name" = 'something' where "name" = 'else';

Question 79

SQL-UPDATE Why is it important to include a where clause in your update statements?

Answer 79

so you dont accidentally chage the entire column

Question 80

SQL-DELETE How do you delete rows from a database table?

Answer 80

delete from "table" where "name" = 'something' returning *; <-- returning clause is optional

Question 81

SQL-DELETE How do you accidentally delete all rows from a table?

Answer 81

delete from "table";

Question 82

SQL-JOIN What is a foreign key?

Answer 82

a foreign key is a column used in another table to link them

Question 83

SQL-JOIN How do you join two SQL tables?

Answer 83

use the join clause select * from "thisTable" join "thisOtherTable" using ("thisColumn");

Question 84

SQL-JOIN How do you temporarily rename columns or tables in a SQL statement?

Answer 84

use alias, can use them for more than just select statements select "firstName" as "first" from "thisTable" as "table" join "otherTable" as "other";

Question 85

SQL-AGGREGATES What are some examples of aggregate functions?

Answer 85

MIN, MAX, SUM

Question 86

SQL-AGGREGATES What is the purpose of a group by clause?

Answer 86

to group data that has unique values

Question 87

ES6-PROMISES What are the three states a Promise can be in?

Answer 87

pending, fulfiled or rejected

Question 88

ES6-PROMISES How do you handle the fulfillment of a Promise?

Answer 88

promise.then and pass a callback function

Question 89

ES6-PROMISES How do you handle the rejection of a Promise?

Answer 89

promise.catch and pass a callback function

Question 90

ARRAY-FILTER What is Array.prototype.filter useful for?

Answer 90

Creating a new array while excluding some elements.

Question 91

ARRAY-MAP What is Array.prototype.map useful for?

Answer 91

Creating a new array containing the transformed elements of another.

Question 92

ARRAY-REDUCE What is Array.prototype.reduce useful for?

Answer 92

Combining the elements of an array into a single value.

Question 93

ES6-CLASSES What is "syntactic sugar"?

Answer 93

syntax that is designed to make things easier to read or to express.

Question 94

ES6-CLASSES What is the typeof an ES6 class?

Answer 94

functions

Question 95

ES6-CLASSES Describe ES6 class syntax.

Answer 95

``` class someName { constructor (var1, var2, var3) { this.var1 = var1; this.var2 = var2; this.var3 = var3; } ``` someFunction() { } }

Question 96

ES6-CLASSES What is "refactoring"?

Answer 96

restructuring code without changing the purpose of the original code

Question 97

WEBPACK-INTRO What is Webpack?

Answer 97

it is a module bundler for JS that transforms html, css, and images. Webpack takes modules with dependencies and generates static assets representing those modules.

Question 98

WEBPACK-INTRO How do you add a devDependency to a package?

Answer 98

use --save-dev in the command line | ex: npm install --save-dev webpack

Question 99

WEBPACK-INTRO What is an NPM script?

Answer 99

way to bundle common shell commands for your project

Question 100

WEBPACK-INTRO How do you execute Webpack with npm run?

Answer 100

npm run build

Question 101

ES6-MODULES How are ES Modules different from CommonJS modules?

Answer 101

ES Module = standard for JS ex: import, export CommonJS = default for Node.js ex: require

Question 102

ES6-MODULES What kind of modules can Webpack support?

Answer 102

ECMAScript, CommonJS, and AMD module

Question 103

REACT-ELEMENTS What is React?

Answer 103

a library for building UIs. React makes it easy to create interactive UIs.

Question 104

REACT-ELEMENTS What is a React element?

Answer 104

a react element is what gets returned from components | a plain js object.

Question 105

REACT-ELEMENTS How do you mount a React element to the DOM?

Answer 105

``` const root = ReactDOM.createRoot(container); root.render(div); ```

Question 106

BABEL-INTRO What is Babel?

Answer 106

it is a compiler that transforms es6 JS to es5 JS to make it backwards compatible

Question 106

BABEL-INTRO What is a Plug-in?

Answer 106

it is a software addon that enhances the program

Question 107

BABEL-INTRO What is a Webpack loader?

Answer 107

allow you to pre-process files as you import or “load” them

Question 108

BABEL-INTRO How can you make Babel and Webpack work together?

Answer 108

use npm i --save-dev babel-loader babel compiles the code and webpack runs the code

Question 109

REACT-JSX What is JSX?

Answer 109

syntax extension to JavaScript that produces react "elements", structures UI similar to html

Question 110

REACT-JSX Why must the React object be imported when authoring JSX in a module?

Answer 110

because internally every JSX is creating a React Component using JSX transformer

Question 111

REACT-JSX How can you make Webpack and Babel work together to convert JSX into valid JavaScript?

Answer 111

npm i --save-dev webpack npm i --save-dev babel-loader npm i --save-dev @babel/plugin-transform-react-jsx

Question 112

REACT-FUNCTION-COMPONENTS What is a React component?

Answer 112

it is a function or a class whose job is to return react elements

Question 113

REACT-FUNCTION-COMPONENTS How do you define a function component in React?

Answer 113

just like any other function but with first letter capital, but return what looks like html ``` function CustomButton() { return <.button>Click Me! <./button>; (remove dots. brainscape dont allow) } ```

Question 114

REACT-FUNCTION-COMPONENTS How do you mount a component to the DOM?

Answer 114

``` const container = document.querySelector('#root'); const root = ReactDOM.createRoot(container); ``` root.render(<.CustomButton />);

Question 115

REACT-PROPS-AND-EXPRESSIONS What are props in React?

Answer 115

Props (properties) are arguments passed into React components through HTML attributes

Question 116

REACT-PROPS-AND-EXPRESSIONS How do you pass props to a component?

Answer 116

by typing it with the react component ``` ex: function CustomButton(props) { console.log(props.name) return {props.text}; } ``` <.CustomButton text="something" name="andy" />

Question 117

REACT-PROPS-AND-EXPRESSIONS How do you write JavaScript expressions in JSX?

Answer 117

within curly braces { } | curly braces are how we escape JSX syntax into JS syntax

Question 118

REACT-CLASS-COMPONENTS How do you create "class" component in React?

Answer 118

``` class Something extends React.Component { render(props) { return <.button> { props.text } <./button> } } ```

Question 119

REACT-CLASS-COMPONENTS How do you access props in a class component?

Answer 119

???

Question 120

REACT-EVENTS-AND-STATE What is the purpose of state in React?

Answer 120

to store information or data of react components

Question 121

REACT-EVENTS-AND-STATE How do you pass an event handler to a React element?

Answer 121

pass as props (camelCase) pass the function ex: <.button onClick={this.function}><./button>

Question 122

REACT-FORM-CONTROLS What are controlled components?

Question 123

REACT-FORM-CONTROLS What two props must you pass to an input for it to be "controlled"?

Question 124

REACT-RENDERING-LISTS What Array method is commonly used to create a list of React elements?

Answer 124

map method

Question 125

REACT-RENDERING-LISTS What is the best value to use as a "key" prop when rendering lists?

Question 126

EXPRESS-STATIC What does express.static() return?

Answer 126

returns an object

Question 127

EXPRESS-STATIC What is the local __dirname variable in a Node.js module?

Answer 127

tells you the absolute path of the directory containing the currently file

Question 128

EXPRESS-STATIC What does the join() method of Node's path module do?

Answer 128

join combines directories into an absolute file path

Question 129

FETCH What does fetch() return?

Answer 129

fetches a resource from the network and returns a promise which is fulfilled once the response is available

Question 129

FETCH What is the default request method used by fetch()?

Answer 129

a get request

Question 130

FETCH How do you specify the request method (GET, POST, etc.) when calling fetch?

Answer 130

as the second optional parameter of fetch | ex: fetch ('someLink', {method: post})

Question 131

FETCH-IN-REACT When does React call a component's componentDidMount method?

Answer 131

immediately after a component is mounted (inserted into the dom tree)

Question 132

FETCH-IN-REACT Name three React.Component lifecycle methods.

Answer 132

componentsDidMount( ), componentsDidUpdate( ), componentWillUnmount( )

Question 133

FETCH-IN-REACT How do you pass data to a child component?

Answer 133

by using props to pass data