Experimenting with Javascript Objects (Part 1)

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What is a Javascript Object?

Working with Objects

Defining/Mutating Properties

  • Define them using an object literal during initialization
  • Use the assignment operator
  • Use Object.defineProperty
  • Reflect.defineProperty

Accessing Properties

  • Use for…in
    for…in will loop over all enumerable properties, even those contained in the prototype chain. Non-enumerable properties will not be listed.
> hi mom
> hello world
  • Use Object.keys
    Object.keys will only loop over enumerable properties contained in the object itself, it will not traverse the prototype chain.
  • Use Object.getOwnPropertyNames
    Object.getOwnPropertyNames will loop over all enumerable and non-enumerable properties in the object itself, it will not check the prototype chain.

Deleting Properties

  • Use the delete keyword
  • Use Reflect.deleteProperty

Const vs Let vs Var

Javascript Objects are references

Functions are Objects

Arrays are Objects

> [1, 2, 3, hello: 'world', hi: 'mom']
> key: 0
> key: 1
> key: 2
> key: hello
> value: 1
> value: 2
> value: 3

Prototype Chain

myObject <- Object.prototype <- null
  • Date objects inherit from Date.prototype
myDateVariable <- Date.prototype <- Object.prototype <- null
  • Array objects inherit from Array.prototype
myArrayVariable <- Array.Prototype <- Object.prototype <- null
  • myObject objects inherit from myObject.prototype
myObject <- Object.prototype <- null
myObject <- myObjectFunc.prototype <- Function.prototype <- Object.prototype <- null
  1. Creating a new object
  2. Setting the prototype of this object to the constructor function’s prototype property
  3. Binding the this keyword to the newly created object and executing the constructor function
  4. Returning the newly created object

Assigning a Prototype to an Object

mySecondObject <- myFirstObject <- Object.prototype <- null

Prototypal Inheritance and Prototypal Delegation

Inheriting methods and the “this” keyword

Property Shadowing





Frontend Software Engineer at Blitz App— Founder of GDLauncher

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Davide Ceschia

Davide Ceschia

Frontend Software Engineer at Blitz App— Founder of GDLauncher

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