The Observer Pattern in software engineering features two main components: the subject, which manages its observers, and the observer, which reacts to notifications from the subject. This pattern promotes loose coupling, enabling independent modifications and easy addition of new observers, thus enhancing system flexibility. It is commonly used in event-driven architectures, making it a versatile solution for applications requiring multiple object updates from a shared data source.

1. JAVASCRIPT
Observer Pattern

2. The observer pattern, frequently
employed in software engineering,
especially in event-driven
architectures, comprises two core
elements: the Subject and the
Observer. The Subject oversees its
observers, informing them of any
status changes. Conversely, the
Observer actively awaits
notifications from the Subject and
responds as needed.
INTRODUCTION

3. 01
The Observer Pattern allows for
flexible communication between
objects, promoting adaptability
and ease of testing within the
codebase.
Loose Coupling
02
The Observer Pattern cleanly
separates observer and subject
responsibilities, simplifying
modifications or extensions to each
component independently.
Separation of Concern
03
The Observer Pattern simplifies
adding new Observers without
altering existing components,
enhancing system flexibility for
feature incorporation.
Extensibility
04
The Observer Pattern is widely used
when multiple objects require
updates from a shared data
source, offering versatility and
widespread adoption across
applications.
Reusability
ADVANTAGES

4. CODE EXAMPLE
// Define the Subject
class Subject {
constructor() {
this.observers = []; // Initialize empty list of observers
}
subscribe(observer) {
this.observers.push(observer); // Add an observer to the list
}
unsubscribe(observer) {
this.observers = this.observers.filter(obs => obs !== observer); // Remove the observer from the list
}
notify(data) {
this.observers.forEach(observer => observer.update(data)); // Notify all observers of the change
}
}
// Define the Observer
class Observer {
update(data) {
console.log('Data changed:', data); // Take action in response to change
}
}
// Usage
const subject = new Subject();
const observer1 = new Observer();
const observer2 = new Observer();
subject.subscribe(observer1);
subject.subscribe(observer2);
subject.notify('hello world'); // Output: "Data changed: hello world"
subject.unsubscribe(observer1);
subject.notify('goodbye'); // Output: "Data changed: goodbye"

5. 72%
SALFORD & CO.
wwww.studysection.com
support@studysection.com
CONTACT US