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Object Instantiation

Object Instantiation

In Javascript and most other languages, an object contains a series of properties, which are a key, value pair. There are multiple options available to you when you need to construct an object.

Initialize an object variable

You can create an object with pre-defined properties like so:

let myObject = {
  name: "Dave",
  age: 33
}

Creating an empty object

This creates an empty object inside our myObject variable:


let myObject = new Object();

When you wish to add properties to your object, you simply use either dot notation or bracket notation with the property name of your choice:


myObject.name = "Johnny Mnemonic"
myObject["age"] = 55

Using a constructor function

You can define a constructor function that you can use to create your objects:


function Kitten(name, cute, color) {
  this.name = name,
  this.cute = cute,
  this.color = color
}

You can define a variable containing an instantiation of this object by calling the constructor function:


let myKitten = new Kitten("Nibbles", true, "white")

Object.create()

The Object.create() method (first defined in ECMAScript 5.1) allows you to create objects. it allows you to choose the prototype object for your new object without needing to define a constructor function beforehand.

// Our pre-defined object
let kitten = {
  name: "Fluff",
  cute: true,
  color: "gray"
}
// Create a new object using Object.create(). kitten is used as the prototype
let newKitten = Object.create(kitten)

console.log(newKitten.name) // Will output "Fluff"

More Information

MDN article on working with objects

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