Objects in JavaScript

Basics of Objects

Emily Y Leung
3 min readSep 2, 2023

Field notes while going through the JavaScript Roadmap

Photo by Luca Bravo on Unsplash

What is an Object?

An Object in JavaScript is a data type that stores a collection of properties in key-value pairs. Each key-value pair is used to define characteristics of any arbitrary item.

The key of an Object must be a string, whereas the value can be of any data type (including another object, or function — also known as a method).


  • A pen has several properties such as colour, brand, material, etc.
let pen = {
colour: "black",
brand: "Pilot",
material: "metal"

How can we create objects?

There are two ways which we can do this:

  1. Create an object via the constructor
let user = new Object();

2. Using the object literal syntax

let user = {};

How can we assign a property in an object?

There are two ways we can assign a property to an object:

  1. Dot syntax
let user = {};

user.age = 25;