My node.js journey

module

• CommonJS, every file is module (by default)

• Modules - Encapsulated Code (only share minimum)

• if we console.log(module) we will get the module object

• we can import the module by using require()

• we can export the module by using module.exports

• if we import module without assigning it to a variable, we will get the default export

• if immediately invoked function expression (IIFE) is used or the module is imported without assigning it to a variable, the module will be executed immediately

• built in modules in node.js- OS, PATH, FS , HTTP

• OS module - provides a way to interact with the operating system

• create your own module by using exports.functionName = function(){}

const os = require("os");

// info about current user
const user = os.userInfo();
console.log(user);

// method returns the system uptime in seconds
console.log(`The System Uptime is ${os.uptime()} seconds`);

const currentOS = {
  name: os.type(),
  release: os.release(),
  totalMem: os.totalmem(),
  freeMem: os.freemem(),
};
console.log(currentOS);

• PATH module - provides a way to interact with the file system
• FS module - provides a way to interact with the file system
• both async and sync methods are available
• HTTP module - provides a way to interact with the HTTP protocol

//just a basic server
const http = require("http");

const server = http.createServer((req, res) => {
  res.write("welcome to our page");
  res.end();
});

server.listen(3000);

• req.url - returns the url of the request
• npx is package runner
• why package.lock file?
• force other user use the exact version of the package
• semantically versioning - versioning that is based on the order of changes
• major.minor.patch

Event loop

• event loop allows node to perform non-blocking i/o operations- despite the fact htat js is single threaded

• by offloading oprations to the https://nodejs.dev/learn/the-nodejs-event-loop https://www.youtube.com/watch?v=PNa9OMajw9w

  • js read line by line

console.log("first task");
console.time();
setTimeout(() => {
  console.log("second task");
}, 0);
console.timeEnd();
console.log("third task");

• in setInterval it will run every given time and it will run forever
• in setTimeout it will run after given time and it will run only once
• always try to setup assynchronous while making server / rest api routes

Status codes

100 range - informational 200 range - success 300 range - redirect 400 range - client error 500 range - server error