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  • 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
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      • Callbacks
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      • var, let, and const
      • Fetch API (function)
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      • 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. JavaScript Objects & Arrays
  2. Introducing JavaScript objects

Objects

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Last updated 4 years ago

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Nearly all objects in JavaScript are instances of ; a typical object inherits properties (including methods) from Object.prototype, although these properties may be shadowed (a.k.a. overridden). However, an Object may be deliberately created for which this is not true (e.g. by ), or it may be altered so that this is no longer true (e.g. with ).

Changes to the Object prototype object are seen by all objects through prototype chaining, unless the properties and methods subject to those changes are overridden further along the prototype chain. This provides a very powerful although potentially dangerous mechanism to override or extend object behavior.

The Object constructor creates an object wrapper for the given value.

  • If the value is or , it will create and return an empty object.

  • Otherwise, it will return an object of a Type that corresponds to the given value.

  • If the value is an object already, it will return the value.

When called in a non-constructor context, Object behaves identically to new Object().

See also the .

Object
Object.create(null)
Object.setPrototypeOf
null
undefined
object initializer / literal syntax