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express_crashCourse.md

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Express JS Framework

  • It's fast and unopinionated and minimalist web framework for node.js
  • Express is a server-side or back-end framework
  • It is used with react, angular, or vue to be used in combination to build full stack applications.

What to know first

  • JavaScript fundamentals (Object, arrays, Conditions)
  • Basic Node.js & NPM

Must have knowledge on

  • HTTP status codes
  • JSON
  • High Order Array methods - forEach, map, filter
  • Arrow Functions

Basic Route Handling

  • app.get(), app.post(), app.put(), app.delete()
  • Access to params, query strings, url parts
  • Express has a router so we can store routes in separate files and export
  • We can parse incoming data with the Body Parser
app.get('/', function(req, res) {
  // Fetch from database
  // Load pages
  // Return JSON
  // Full access to request and response
});
  • We can set the routing structure by ourselves, follow this code
// creating the route config
app.get('/', (req, res) => {
  res.sendFile(path.join(__dirname, 'public', 'index.html'));
});
  • But we will use static folder path
// Set Static Folder
app.use(express.static(path.join(__dirname, 'public')));
  • By using the static folder path system we can simply just put any file on the static folder and without configure the routes we can access them

Express Middleware

  • These are functions which have access to the request and response object.

  • Express has it's own middleware

  • Execute any code

  • Make changes to the request/response objects

  • End response cycle

  • call next middleware in the stack

  • Middleware functions should have three parameters req, res, next

  • When our server gets request the middleware fires up

Install express

npm install express

Template for Express

  • We will be using express-handlebars as view engine for express.

  • In handlebars whatever we want to output we need to use {{{}}} and to use variable we need to use {{}}

  • Syntax:

// Handlebar Middleware
app.engine('handlebars', exphbs());
app.set('view engine', 'handlebars');

// Homepage Route
app.get('/', (req, res) => res.render('index'));

Extra

  • entry point is the index

  • there are lots of function we need to specify the port which will be listened by the express server. We need to specify the port number.

  • We will be using nodemon to prevent restarting the server again and again

  • We can use custom scripts to define new task

  • mainly we use express to create json api to connect front end to back end or render template where we can use dynamic data to create a dynamic app rather than just a static website.

  • To run the server

npm run dev

  • I am not sure but files that are used as models are always uppercase.

  • We will be using moment to handle the date.

  • Here, this code will give us req.params.id as string but on our member.id which is a integer so our output will come out as void or [], aslo note that we have '===' which will catc that whether it's input and output are same or not. So we will have empty output.

res.json(members.filter(member -> member.id === req.params.id))

  • To solve this conflict we use parseInt(req.params.id)

  • API also stands for those who serves the json

  • Create Member: Whenever we want to create something on the server we need to make a post request to the server. We want to send data and when we will get data we will have it in the req object

  • To get the request successfull we need a body parser

  • This body parser can be identified by a middleware.

  • To work with the back end we might do two things

    • we built an api to view some thing on the fornt end just serving json
    • or we gonna have a complete server side app where we use templates.