Object Properties Explained

In JavaScript, an object is a collection of key-value pairs. These key-value pairs are called properties. The 'key' (also called the property name) is typically a string (though it can be a Symbol), and the 'value' can be any valid JavaScript data type, including:

• Primitive values (strings, numbers, booleans, null, undefined)
• Other objects
• Arrays
• Functions

Think of an object as a container that holds related data and functionality together. The properties define the characteristics and behaviors of the object.

Defining, Accessing, Modifying, and Deleting Properties

Defining Properties

There are several ways to define properties in a JavaScript object:

Object Literal Notation

 const person = {
                    firstName: "John",
                    lastName: "Doe",
                    age: 30,
                    greet: function() {
                        console.log("Hello, my name is " + this.firstName);
                    }
                }; 

This is the most common and concise way to create objects and define their properties.

Dot Notation

 const car = {};
                car.make = "Toyota";
                car.model = "Camry";
                car.year = 2023; 

You can add properties to an existing object using dot notation. If the property doesn't exist, it's created.

Bracket Notation

 const animal = {};
                animal["species"] = "Dog";
                animal["breed"] = "Golden Retriever"; 

Bracket notation is useful when the property name is stored in a variable or contains characters that are not valid in dot notation (e.g., spaces or special characters).

Accessing Properties

You can access property values using either dot notation or bracket notation:

Dot Notation

 console.log(person.firstName); // Output: John
                console.log(car.year); // Output: 2023 

Bracket Notation

 console.log(person["lastName"]); // Output: Doe
                console.log(animal["species"]); // Output: Dog

                const propertyName = "age";
                console.log(person[propertyName]); // Output: 30 (using a variable) 

Modifying Properties

You can change the value of an existing property using assignment:

Dot Notation

 person.age = 31; // Changes the age to 31
                console.log(person.age); // Output: 31 

Bracket Notation

 animal["breed"] = "Labrador"; // Changes the breed to Labrador
                console.log(animal["breed"]); // Output: Labrador 

Deleting Properties

You can remove a property from an object using the delete operator:

Dot Notation or Bracket Notation

 delete person.age; // Removes the age property
                console.log(person.age); // Output: undefined (property no longer exists)

                delete animal["breed"]; // Removes the breed property
                console.log(animal["breed"]); // Output: undefined 

Deleting a property removes it entirely from the object. Accessing a deleted property will return undefined.