Object Properties and Methods in JavaScript

In JavaScript, objects are key to understanding and manipulating data structures. They store collections of property-value pairs, where properties can include attributes and methods. This leds to defining methods, utilizing hasOwnProperty(), employing the delete operator, enumerating properties, and leveraging getter and setter functions, alongside Object.defineProperty() and property descriptors.

Defining Methods in Objects

Methods are functions associated with an object, allowing objects to act and interact. They are defined just like any other property, but their values are functions.

let person = {
  name: "John",
  greet: function() {
    console.log("Hello, " + this.name);

person.greet(); // Outputs: Hello, John


The hasOwnProperty() method checks if an object has a property as its own (not inherited).

let person = {
  name: "John"

console.log(person.hasOwnProperty("name")); // true
console.log(person.hasOwnProperty("toString")); // false, because it's inherited

delete Operator

The delete operator removes a property from an object.

let person = {
  name: "John"

delete person.name;
console.log(person.name); // undefined

Enumerating Properties

You can enumerate (loop through) an object’s properties using for...in loop.

let person = {
  name: "John",
  age: 30

for (let prop in person) {
  console.log(prop + ": " + person[prop]);
// Outputs: name: John and age: 30

Getter and Setter Functions

Getters and setters allow you to define methods that are accessed like properties. This can be useful for encapsulation or when you want to run some code before getting or setting a value.

let person = {
  firstName: "John",
  lastName: "Doe",
  get fullName() {
    return `${this.firstName} ${this.lastName}`;
  set fullName(name) {
    [this.firstName, this.lastName] = name.split(' ');

console.log(person.fullName); // John Doe

person.fullName = "Jane Doe";
console.log(person.fullName); // Jane Doe

Object.defineProperty() and Property Descriptors

Object.defineProperty() allows you to define a new property directly on an object, or modify an existing property, and specify its configurability.

let person = { name: "John" };

Object.defineProperty(person, "age", {
  value: 30,
  writable: true,
  enumerable: true,
  configurable: true

console.log(person.age); // 30

Property descriptors include:

  • value: The value of the property.
  • writable: If true, the property’s value can be changed.
  • enumerable: If true, the property shows up during enumeration.
  • configurable: If true, the property can be deleted and its descriptor can be changed.


JavaScript objects are versatile and powerful, allowing for complex data structures and interactions. Understanding how to define methods, check for properties, manipulate properties, and use getter/setter functions, along with the capabilities of Object.defineProperty(), equips you with the tools to create more sophisticated and controlled code structures. These concepts are foundational in JavaScript programming, enabling detailed manipulation and access control over object properties.