Aggregation in JavaScript

Aggregation is a fundamental concept in object-oriented programming that facilitates the creation of complex objects by combining simpler ones. It establishes a “has-a” relationship between objects, where one object contains references to other objects as its components. This relationship enhances code reusability and modularity in JavaScript applications.

Approach 1: Aggregation using Object Properties

• Create an object that contains properties representing the components you want to aggregate.
• These properties can be references to other objects, functions, or any data type.
• Establish an aggregation relationship by including one object within the other as a property.
• Allow one object to reference and use another, providing a way to model aggregation.

Example: In this example, we showcase aggregation in JavaScript with two book objects, book1 and book2, aggregated within a library object, GFG. The library object has methods to add books dynamically and display their information. A third book, book3, is added to the library, and the display method is used to show details of all the books in the library.

Javascript

const book1 = {
    title: "The Great Gatsby",
    author: "F.Scott Fitzgerald"
};
const book2 = {
    title: "The GeeksforGeeks",
    author: "Geek"
};

// Create an object representing a library that
// aggregates books
const GFG = {
    name: "My Library",
    books: [book1, book2],
    addBook: function (book) {
        this.books.push(book);
    },
    displayBooks: function () {
        console.log(`Books in ${this.name}:`);
        this.books.forEach((book, index) => {
        console.log(
        `${index + 1}. Title: ${book.title}, Author: ${book.author}`);
        });
    }
};

// Add more books
const book3 = {
    title: "2023",
    author: "George Orwell"
};
GFG.addBook(book3);

// Display the books
GFG.displayBooks();

Output

Books in My Library:
1. Title: The Great Gatsby, Author: F.Scott Fitzgerald
2. Title: The GeeksforGeeks, Author: Geek
3. Title: 2023, Author: George Orwell

Approach 2 : Aggregation using Arrays

• Create an object that contains an array property to hold aggregated items.
• Perform operations like adding, removing, or manipulating items within the array.
• Aggregation starts with collecting data from various sources, such as user input, databases, or external files.
• Typically, store the collected data in an array data structure capable of holding multiple values of the same type.
• Arrays provide a way to represent a collection of related data items.
• Each item in the array is stored at a specific index, allows easy access and manipulation of individual elements.
• Arrays are often used to group and classify data, allowing effective organization, such as storing scores of students in a class.

Example: In this example, player objects are created using a constructor function, and a team object is formed to aggregate these players. The team object includes methods to add, remove, and display players. Additional players are added, the team is displayed, a player is removed, and the updated team is displayed.

Javascript

function Players(name, age) {
    this.name = name;
    this.age = age;
}

// Create Player objects
const player1 = new Players("Kumar", 31);
const player2 = new Players("Bob", 29);
const team = {
    name: "Red Team",
    players: [player1, player2],
    addPlayer: function (player) {
        this.players.push(player);
    },
    removePlayer: function (playerName) {
        const indexToRemove =
            this.players.findIndex(player => player.name === playerName);
        if (indexToRemove !== -1) {
            this.players.splice(indexToRemove, 1);
        }
    },
    displayTeam: function () {
        console.log(`Team: ${this.name}`);
        console.log("Players:");

        this.players.forEach((player, index) => {
            console.log(
            `${index + 1}. Name: ${player.name}, Age: ${player.age}`);
        });
    }
};

// Add more players to the team
const player3 = new Players("Raj", 32);
team.addPlayer(player3);

// Display the team and its players
team.displayTeam();
team.removePlayer("Bob");

// Display the updated team
team.displayTeam();

Output

Team: Red Team
Players:
1. Name: Kumar, Age: 31
2. Name: Bob, Age: 29
3. Name: Raj, Age: 32
Team: Red Team
Players:
1. Name: Kumar, Age: 31
2. Name: Raj, Age: 32