04-database-basics

Database Basics

Database Systems

• MongoDB
• MySQL
• SQL Server
• Oracle
• MariaDB
• PostgreSQL
• CouchDB
• etc...

CRUD

• Create, Read, Update, Delete
• each item in the collection is a document
• Create an item to insert document in mongoDB
• Read performs quesry on the collection, reading, loading or retrieving data from the database
• Update means edit or update an existing document
• Delete to remove/delete a document

Setup App

• npm install express then require it
• let the app listen to port 3000
• app.use(express.urlencoded({extended: false})) is used to enabling the feature in express so that the user's input is easily accessible from request body object
• npm install nodemon to automatically restart for every changes you made
• add "watch": "nodemon server" script in package.json so you can run npm run watch in the terminal
• insertOne method means create in CRUD operation that accepts two (2) arguments
  • 1st: is an object to be stored as document in the database
  • 2nd: is a function to be call once the item is created in the database
• npm install mongodb which is driver/package, official package that gives Node.js the ability work w/ mongoDB database
• connect is a mongoDB method that accepts three (3) arguments
  • 1st: is a connection string to tell mongoDB what or where we want to connect to
  • 2nd: in an object set mongoDB configuration {useNewUrlParser: true}
  • 3rd: is a function that the connect method will call after it connected to the database, it accepts parameter
    • 1st: err, if there is an error while connecting
    • 2nd: client that contains information about the mongoDB environment that we just connected to
• find method to read data in the database, leave it blank for all documents
• toArray method converts the data into a javaScript array, it accepts a function as an argument and will call the function when database action completes, the function will have two (2) parameters
  • 1st: error parameter to make sure there is no error reading from the database
  • 2nd: javaScript array of all items from the database
• redirect method to redirect the user of the app
• app.use(express.static('public')) this will make the contents of the folder available from the root of the server
• the parameter in the event listener contains all sorts of information about the event
• axios keeps the code clean and minimal
• post method of axios library is how we can send in on the fly post request to a server, with two (2) arguments
  • 1st: is the url that we want to send a post request to
  • 2nd: is a javaScript object which is the data that will be sent along w/ the request to that url (the data that server will receive)
• then method with a function that will not run until the action is complete
• catch method with a function that will run if the action runs into a problem
• findOneAndUpdate is a CRUD method that will have three (3) arguments
  • 1st: is to tell which document to update
  • 2nd: is to tell what to update on that document
  • 3rd: is a function that will get called once the database action is completed
• data- is a HTML5 attribute that let us embed data in the html
• deleteOne is a CRUD method, with two (2) arguments
  • 1st: is select the document to delete
  • 2nd: is a function that will run after the database action is completed
• submit event takes care both click to submit and pressing enter/return key on the keyboard
• insertAdjacentHTML method with two (2) arguments
  • 1st: is where to add the new HTML, E.g. beforeend
  • 2nd: is HTML we want to add
• JSON is a JavaScript Object Notation which is popular way of sending data back and forth
• Client-Side Rendering means the server would only send the browser raw data, then it would be up to the browser/client to use that raw data to generate the appropriate HTML, instead of generating each HTML for our dynamic data on the server side and then sending that HTML out to the web browser
• JSON.stringify method converts javaScript data into a string of text

Security

• set method with two (2) arguments
  • 1st: string of text (WWW.Authenticate)
  • 2nd: is a name of application, a string of text (Basic realm="Simple App")
• status method to add an a code status
• 401 code status means unathorized
• npm install sanitize and require it
• sanitizedHTML with two (2) arguments
  • 1st: is the text/input to sanitize or clean up
  • 2nd: is an object for options, empty array and object to not allow any HTML tags & attributes (allowedTags: [], allowedAttributes: {})

Deploying App

• check if git is installed git --version
• set a basic information git config --global user.name and git config --global user.email
• install heroku then enter credentials in terminal heroku login
• add a .gitignore file to ignore files like node_modules folder to save some bandwidth
• git init to initialize a git on a project
• git add -A to add all the files in git
• git commit -m "FIrst commit" to commit files in git with message