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Let's write Code

Let's write Code

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Kapil Sarkar
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FOR RUNNING NODE-JS APPLICATION WE REQUIRE :

  • We need to have Node-JS installed on our system. Node-JS includes the Node-JS runtime and NPM

NODE-REPL :

  • REPL(READ EVALUATE PRINT LOOP)

  • The Node REPL is a powerful tool for Node.js developers, providing a quick and interactive way to experiment with code.

  • If we write on our terminal node

  • Output

  •   Welcome to Node.js v18.12.1.

  • Basically it enters into a program , a kind of C++ like program or it's a kind of Node REPL.

  • Over here in piece of Node-JS code will work.

  • Example :

       2+3
   Output :
   5

  let i = 20
  let j = 30
  i + j
  Output :
  50

  console.log("Kapil")
  Output:
  Kapil

  • We are running java script code on the Node runtime environment.

  • So Node-JS is a Java Script run time environment.

EXECUTION OF THE CODE :

  • Whenever we write any piece of Java Script code Node-JS passes the code to the V8 engine then V8 engine executes the code.

  • This whole process is known as Node REPL.

  • The code which we are running on the terminal is very similar to running the code on the browser console.

  • For running java script code on VS CODE Terminal write :

node app.js
  • Here app.js is the name of the file.

GLOBAL OBJECT :

  • window is the global object given by the browser.

  • On the browser console this also refers to the window object.

  • In the VS CODE if we write :

console.log(global)
Output :

<ref *1> Object [global] {
  global: [Circular *1],
  queueMicrotask: [Function: queueMicrotask],
  clearImmediate: [Function: clearImmediate],
  setImmediate: [Function: setImmediate] {
    [Symbol(nodejs.util.promisify.custom)]: [Getter]
  },
  structuredClone: [Function: structuredClone],
  clearInterval: [Function: clearInterval],
  clearTimeout: [Function: clearTimeout],
  setInterval: [Function: setInterval],
  setTimeout: [Function: setTimeout] {
    [Symbol(nodejs.util.promisify.custom)]: [Getter]
  },
  atob: [Function: atob],
  btoa: [Function: btoa],
  performance: Performance {
    nodeTiming: PerformanceNodeTiming {
      name: 'node',
      entryType: 'node',
      startTime: 0,
      duration: 54.420299999881536,
      nodeStart: 3.643099999986589,
      v8Start: 8.012600000016391,
      bootstrapComplete: 40.96389999985695,
      environment: 26.332500000018626,
      loopStart: -1,
      loopExit: -1,
      idleTime: 0
    },
    timeOrigin: 1724845640522.583
  },
  fetch: [AsyncFunction: fetch]
}

  • global is not a part of our V8 engine. It is one of the superpower which is given to us by Node-JS.

  • global object gives us access to many features example : setTimeout ,setInterval and many others.

  • In VS Code if we write

  •   console.log(this)
  Output:
  {} //It represents an empty object
  • In browser console if we type this it points us to the window object.

globalThis :

  • globalThis is referring to global this across all java script runtime.

  • In VS Code if we write

console.log(globalThis)
Output :
similar to console.log(global)
  • In other words globalThis and this represent same this. So if we write :
console.log(globalThis === global)
Output :
true
#nodejs #javascript