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Node

  • Node is a runtime environment to run the javascript outside of the browser.It is not a framework/ programming language.
  • Web browser have js engine to run js code. Node use chromium based js engine v8 (chrome engine) at its core with lot of inbuilt module.
  • Node is single threaded, asynchronus and prefered for cpu intensive task like file read, video upload ect.,
  • NPM : Node Package manager - help us to download package to use in application. It comes along with node.
  • npm install or i package-name : to install latest package.
  • npm install or i package-name@version-number : to install particualr version of package.
  • npm install or i -g package-name : to install package globally.
  • npm init --yes : to initialize a application with package.json file which keep track of dependencies/ installed package and script etc.,
  • npm list : to list all dependencies ('--depth=0') used to give high level dependencies.
  • npm un package-name : to uninstall packages
  • npm update : to update to the semantic versioning we provided
  • every node package has version like this major.minor.patch (2.33.11)
    • major : the feature will cause damage to existing application
    • minor : the feature won't cause damage to existing application
    • patch : bug fixes.
  • ^3.23.2 = 3.23.x (it will install latest package with latest patch).
  • ~3.23.2 = 3.x.x (it will install latest package with latest patch and minor version)
  • npm outdated : to give the details of outdated package
  • npm -g outdated : to give the details of outdated globall package
  • package-lock.json : store the exact version installed in the application.
  • ncu : to update package
  • ncu -u : to update package and make change in package.json
  • npm i package-name --save-dev : to store the dependencies for development and not for deployment / production.
  • npm login : to login to npm registry.
  • npm publish : to publish to npm registry.
  • npm version major/minor/patch : to update existing package.
  • We are using commonJs as module type so we need to export.module and import using require
  • If Es6 we can export using export and import using from like react but need to have extension ".mjs"

Node package

  • nodemon : when working with express we run a server. when making a change we need to start and stop the server.it help to avoid that.
  • node-check-updates / ncu : to monitor / update package to latest version.
  • underscore : is used by developer maths calculation etc.,
  • Joi : Data validation library.

Restful services

  • It is a way/convention to build http service

  • It involves uisng http principle around resource or entity image image image

  • using express which is built in top of the http client make building restful api easy with lot of feature like middleware routes etc.,

Environment variable (window)

  • set : to display all env
  • set key=value : to set a env

Note : set is for storing temporarily

MiddleWare

  • It is a function which help us to process request and give it to next functin in the pipeline and terminate the request by giving response. eg : express.json() : middleware to convert incoming request body into json object.

Mongodb

  • When we set default value to property of model it will be set before hitting database by js.
  • _id aslo set like this by mangodb drive as mongodb don't do anything in making unique.there is a possibility of same id but chance is less
  • objectid has 24 character and it is 12bytes
    • 4 bytes : timestamp ( when created we can use this to get created time).
    • 3 bytes : machine identifier
    • 2 bytes : process identifier
    • 3 bytes : counter ( if all the above bytes are same still we have 2^24 unique document).
  • document embedding is storing the data within the model or collection itself : query faster but redundancy
  • Reference is like only storing the id of other model and later use populate() method to retrive it ; query slower as need to retrive from other collection but reduces redundancy

Design principle :

  • Information expert principle : classes or module having all the information must do expert work eg: chef cooks food with all his knowledge. so instead going for seperated single module put them inside thier respective classes. instead of making a seperated class to cook with all ingredient we can use cook class as it have all details

Test :

Automated test help to test our application by writing and exciting test code with out having to do manual process.There are three types of test

Unit test : Testing unit of code like function with out external dependencies. mostly algorithm and logic function Integration testing : Testing unit of code like function with external dependencies example database, http servers End to end testing : Testing the application through ui example selenium. Prefer to test major flow of application.