Express JS and Node JS in actions. What is Middleware. Client ---> sends a request to our NodeJS http server ---> relays that Request to express JS ----> express generates appropriate response with the help of middleware -> that response is sent through thr node JS http server to the client.
Express Application Generator.
Setup project ->
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npm init - cmd used to scaffold a project. it shows a series of question that u can answer inorder to help setup your project. Result - a package.json file is created.
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nodemon - restarts the server whenever any changes occur in the code. ~hot reload npm install express nodemon (we can add n number of packages separated by space in this command.)
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package.json -> dependencies vs dev dependencies (--save-dev) dev dependency -> required for development. dependency -> required for your application. "type": "module" -> so that we can use es6 modules. Previous versions used to have 'require' // to use es6 with json modules we also need to use this in the scripts section of package.json "scripts": { "start": "nodemon --experimental-json-modules index.js" },
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HTTP request methods and Routes- Routes - How an app responds to a client's request to a particular endpoint. It is basically a routing path and an HTTP method. Routes are simply - Paths & HTTP Methods HTTP Methods - actions taken on a specific resouce. CRUD. e.g. GET, POST, PUT, DELETE. GET - retrieves data from the server. POST - sends data to the server and creates a resouce. PUT - updates an existing resouce on the server. Delete - deletes an existing resource on the server. HTTP Messages - Requests and Responses.
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Routes - Paths & HTTP Methods app.get(
/animals, (req, res) => { res.json(data); }); // Here the 1st argument of app.get() method "/animals" is the path which the client has requested to with an HTTP method (app.get, app.post etc.) // 2nd arg, method - which will be return some data/functionality. -
Routing Parameters - Parts/segments of url that are used to capture values specified at positions within the url. (query) app.get(
/class/:id/student/:stu_id, (req, res) => { res.send(req.params); }); req.params returns the key value pairs of the parameters in the url. -
Route Handlers -
Response Method - .json .send .download - trqansfers a file as an attachment. .redirect
Route Chaning- chaining several methods wiuth the same route to one single method. app.get('/class', callbkGET); app.post('/class', callbkPOST); app.put('/class', callbkPUT); // these can be chained using "app.route" method like this - app.route('/class').get(callbkGET).post(callbkPOST).put(callbkPUT);
############################### Middleware- see the express js definition. Functions that have access to the request and response and the next() method in the application's req response lifecycle. Built in Middleware - Express JS 1. express.static - serves static assets 2. express.json - parses incoming req with JSON payload. 3. express.urlencoded - parses incoming req with url encoded payload.
Security Best practices. keep updating the node version as well as all the packages and express. use TLS. use Helmet - protects your app. sets http headers appropriately and securely. collection of middleware functions that does that. use cookies securely. prevent brute force attack. rate-limiter-flexible. to rate limit ensure your dependencies are secure. npm audit.