Node.js, cmd, React, SQL (senior) Flashcards
What is a CLI?
A command-line interface (CLI) processes commands to a computer program in the form of lines of text. The program which handles the interface is called a command-line interpreter or command-line processor.
What is a GUI?
graphical user interface (GUI) 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.
man
man is an interface to the on-line reference manuals.
cat
concatenate files and print on the standard output
ls
list local directory
pwd
prints name os current working directory
echo
displays a line of text
touch
changes file timstanp
mkdir
make directory
mv
move or rename
rm
remove
cp
copy
What is Node.js?
a backend language that allows javascript to run outside of browser
What can Node.js be used for?
backend for web applications, command line or automation
What is a REPL?
A read–eval–print loop (REPL), also termed an interactive toplevel or language shell, is a simple interactive computer programming environment that takes single user inputs, executes them, and returns the result to the user
When was Node.js created?
may 27 2009
What back end languages have you heard of?
java, c, .net, pascal, python, php
What is a computer process?
a task being run by the computer
Roughly how many computer processes are running on your host operating system (Task Manager or Activity Monitor)?
468
Why should a full stack Web developer know that computer processes exist?
Full stack Web development is based on making multiple processes work together to form one application and knowing about the processing power of each component helps with making a more efficient application
What is a computer process?
the instance of a computer program that is being executed by one or many threads. It contains the program code and its activity.
What is the process object in a Node.js program?
is a global that provides information about, and control over, the current Node.js process.
How do you access the process object in a Node.js program?
by calling process variable
What is the data type of process.argv in Node.js?
array
What is a JavaScript module?
a single .js file that holds everything necessary to execute only one aspect of the program
What values are passed into a Node.js module’s local scope?
exports, require, module, __filename, __dirname
Give two examples of truly global variables in a Node.js program.
global, console, window, process
What is the purpose of module.exports in a Node.js module?
exporting a function from one module so it can be accessed from another
How do you import functionality into a Node.js module from another Node.js module?
by calling require() function and passing the module as the argument
What is the JavaScript Event Loop?
how js queue events and execute them in order by moving tasks from queue to stack
What is different between “blocking” and “non-blocking” with respect to how code is executed?
blocking is when additional process has to wait for to be executed and none blocking allows other events to be executed while processing
What is a directory?
a file system cataloging structure containing refrence to other files and directories
What is a relative file path?
same directory
What is an absolute file path?
refrence to a directory from root
What module does Node.js include for manipulating the file system?
fs
What method is available in the Node.js fs module for writing data to a file?
writefile()
Are file operations using the fs module synchronous or asynchronous?
both
What is JSON?
javascript object notation, it’s data interchange format that can be used to store or extract data from an object
What are serialization and deserialization?
serialized is the string format of the data object
Why are serialization and deserialization useful?
serialized can be transfer over network and deserialized enables interaction with the data inside the object
How do you serialize a data structure into a JSON string using JavaScript?
stringify()
How do you deserialize a JSON string into a data structure using JavaScript?
parse()
What is a client?
service requester
What is a server?
service and resource provider
Which HTTP method does a browser issue to a web server when you visit a URL?
GET
What is on the first line of an HTTP request message?
request method
What is on the first line of an HTTP response message?
status code
What are HTTP headers?
An optional set of HTTP headers specifying the request, or describing the body included in the message.
Is a body required for a valid HTTP message?
it’s optioal
What is NPM?
node package manager, world’s largest software registry
website, cli and registry
What is a package?
it’s bits of reusble codes shared by other developers and it incudes files and directories in it
How can you create a package.json with npm?
using npm init command and -y flag
What is a dependency and how to you add one to a package?
any packge that the app is depeded on, using npm install and the name of the package
What happens when you add a dependency to a package with npm?
the meta tags: the name, tag, version, link and address to the files and directories of that package gets added to package .json
How do you add express to your package dependencies?
by instaling using npm i express
What Express application method starts the server and binds it to a network PORT?
listen() method
How do you mount a middleware with an Express application?
use() method with a specified path
Which objects does an Express application pass to your middleware to manage the request/response lifecycle of the server?
next middleware function
What is the purpose of the Content-Type header in HTTP request and response messages?
specifies the file type based on the file extension
What does express.static() return?
the files that are available to be served within the directory using a function
What is the local __dirname variable in a Node.js module?
absolute path to current module directory
What does the join() method of Node’s path module do?
join all the given path segments together and normalize the resulting path
What is the appropriate Content-Type header for HTTP messages that contain JSON in their bodies?
application/json
What does the express.json() middleware do and when would you need it?
It parses incoming requests with JSON payloads
What is the significance of an HTTP request’s method?
it indicates the routing method of the request which will be responded according to
What is Webpack?
a tool that makes bundling of the js applications possible and supportts both commonjs and esm and can extend to ssets such as images, fonts, and stylesheets
How do you add a devDependency to a package?
by using –save-dev flag while installing the the package or adding it manually to package.json
What is an NPM script?
shell command
How do you execute Webpack with npm run?
by using the command name
How are ES Modules different from CommonJS modules?
they can be run in browser and theyre more compact
What kind of modules can Webpack support?
CommonJS, AMD, ES6 modules
What is React?
A JavaScript library for building user interfaces
What is a React element?
an object that describs type and propps of a
creates and returns a new react element of the type given
How do you mount a React element to the DOM?
by calling render method of reactdom object
What is Babel?
it’s a javascript code compiler
What is a Plug-in?
a preset that allows transformation
What is a Webpack loader?
loaders are transformations that are applied to the source code of a module and allow pre-processing of files as they import or load
How can you make Babel and Webpack work together?
using babel-loader and config file
What is JSX?
it javascript xml a syntax extension to javascript and produces React elements
Why must the React object be imported when authoring JSX in a module?
jsx is for writting elements which would be done using react
How can you make Webpack and Babel work together to convert JSX into valid JavaScript?
by using react-jsx pugin
What is a React component?
isolated, reusable ui pieces
How do you define a function component in React?
by defining a javascript function that returns a JSX element
How do you mount a component to the DOM?
by calling render method of the reactdom object
What are props in React?
optional properties (object) that can be passed into components
How do you pass props to a component?
assigning the value to the key name of the property
How do you write JavaScript expressions in JSX?
by wrapping the variable name or any expression in curly braces
What Array method is commonly used to create a list of React elements?
Map()
What is the best value to use as a “key” prop when rendering lists?
a unique name like: IDs
How do you create “class” component in React?
by extending the react.component and a class name
How do you access props in a class component?
this.props
What is the purpose of state in React?
to keep track of the element changes
How to you pass an event handler to a React element?
by adding {}
What are controlled components?
an element that whose value is controlled by react
What two props must you pass to an input for it to be “controlled”?
onChange and value
What is PostgreSQL and what are some alternative relational databases?
free, open source Relational Database Management System (RDBMS)
MySQL SQL Oracle
What are some advantages of learning a relational database?
it’s easy to create and manage database for data with some relation, data integrity.
What is one way to see if PostgreSQL is running?
checking processes
What is a database schema?
a collection of tables, which defines how the data should be organized
What is a table?
a list of rows each with the same set of attributes
What is a row?
a record with set of attributes on the table
What is SQL and how is it different from languages like JavaScript?
structured query language is the primary way to interact with relational database.
JS is imperative language which has to be told what to do, SQL is declarative which we describe the expected result and programming environment decides how to get that
How do you retrieve specific columns from a database table?
by using select statement, using select keyword passing each column name as a string separated by comma and from keyword passing table name as string and ends the query with ;
How do you filter rows based on some specific criteria?
using where clause at the end of the statement followed by the column name as string = and category name as string
What are the benefits of formatting your SQL?
readability
What are four comparison operators that can be used in a where clause?
< > = !=
How do you limit the number of rows returned in a result set?
using limit clause followed by an integer
How do you add a row to a SQL table?
insert into clause followed by name of table in “” and list of columns in “” in () and values clause folowed by values in ‘’ in ()
What is a tuple?
a list of values
How do you add a row to a SQL table?
insert into clause followed by name of table in “” and list of columns in “” in () and values clause followed by values in ‘’ in ()
How do you add multiple rows to a SQL table at once?
seperated list of tuple by commas
How do you add multiple rows to a SQL table at once?
separated list of tuple by commas
How do you update rows in a database table?
using update clause with name of the table
set clause with name of the column = value
where clause with a id column = value
Why is it important to include a where clause in your update statements?
without where all items in column gets updated
What is a foreign key?
the id value of a row used in a different table
How do you join two SQL tables?
using select follow by column or * for all
from followed by table name
and join by another table name followed by using keyword and the identifier
How do you temporarily rename columns or tables in a SQL statement?
using select followed by nameof the table . name of the column and as keyword with new name
in case of using alias for table names, on the line for from or join add the as keyword followed by alias
How do you delete rows from a database table?
delete clause followed by from keyword and the name of the table
How do you accidentally delete all rows from a table?
by not using where clause to specify which row to delete or “where true”
What are some examples of aggregate functions?
max() avg() count() main() sum() every()
What is the purpose of a group by clause?
to group rows and get a answer about a group of rows without asking the question from every single row
