JS/TS
  • JavaScript Development
  • JS Principles
    • JS Principles
      • Primitive data types
      • typeof operator
      • Scope
      • Hoisting
      • IIFE
      • Closure
      • Anonymous functions in JS
      • Conditional (ternary) operator
        • Coercion vs Conversion
      • Event-driven programming
      • Factory Function
      • JSON.stringify()
      • Strict mode
      • super() keyword
      • What are memory leaks?
      • Micro-tasks within an event loop (Summary)
      • Macro-tasks within an event loop (Summary)
      • null vs undefined
    • Memory Management
    • Advanced function concepts
      • Impure vs Pure Functions
      • Factory functions
  • JavaScript Objects & Arrays
    • Introducing JavaScript objects
      • Build-in objects
        • isNaN()
      • RegExp
        • RegExp.prototype.test()
      • String
        • String.prototype.split()
        • String.prototype.slice()
      • Objects
        • Object.assign()
        • Object.create()
        • Object.defineProperties()
        • Object.defineProperty()
        • Object.entries()
        • Object.freeze()
        • Object.getOwnPropertyNames()
        • Object.getPrototypeOf()
        • Object.isFrozen()
        • Object.isSealed()
        • Map
      • Standard built-in methods to work with Arrays
        • Array.of()
        • Array.prototype.concat()
        • Array.prototype.every()
        • Array.prototype.filter()
        • Array.prototype.find()
        • Array.prototype.findIndex()
        • Array.prototype.forEach()
        • Array.prototype.join()
        • Array.prototype.map()
        • Array.prototype.pop()
        • Array.prototype.shift()
        • Array.prototype.reverse()
        • Array.prototype.some()
        • Array.prototype.sort()
        • Array.prototype.splice()
        • Array.prototype.unshift()
        • Array.prototype.includes()
        • Array.prototype.flatMap()
      • Prototypal inheritance
        • Inheritance with the prototype chain
        • Inheriting "methods"
  • JavaScript Mid
    • JavaScript & ES
      • Arrow Function
      • Anonymous Function
      • Callbacks
      • Promises
      • var, let, and const
      • Fetch API (function)
      • Fetch API
      • Synchronous vs Asynchronous
      • Encapsulation
      • Destructuring assignment
      • call() - apply() - bind()
      • 'This' keyword
      • Functional Programming
  • Browser
    • Event-driven programming
  • TypeScript
    • The TypeScript Handbook
      • Basic Types
      • Interfaces
      • Functions
      • Literal Types
      • Unions and Intersection Types
      • Classes
      • Enums
      • Generics
      • Implements vs extends
  • Hackerrank Practices
    • Practices and examples
  • JS Math
    • Mathematical
      • JavaScript | Math.E() function
      • Math.abs( ) Method
      • Math.ceil( ) function
      • Math floor()
      • Math.imul( ) Function
      • Math log( ) Method
      • Math max()/min() Method
      • Math pow( ) Method
      • Math.sign( ) Function
      • Math sqrt( ) Method
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  1. JS Principles
  2. JS Principles

null vs undefined

  • null is an assigned value. It means nothing.

  • undefined means a variable has been declared but not defined yet.

  • null is an object. undefined is of type undefined.

  • null !== undefined but null == undefined.

null == undefined
true
null === undefined
false
let myLet;
undefined
myLet = 1;
1
myLet = null;
null
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Last updated 4 years ago

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