Can you name the main design patterns used in software development?

Main design patterns commonly used in software development:

• Singleton — ensures that a class has only one instance and provides a global point of access to it.
• Factory Method — defines an interface for creating an object but allows subclasses to alter the type of objects that will be created.
• Observer — allows objects to subscribe to events of another object and receive notifications about changes.
• Decorator — dynamically adds responsibilities to objects by wrapping them.
• Strategy — defines a family of algorithms, encapsulates each one, and makes them interchangeable.
• Adapter — allows objects with incompatible interfaces to work together.

Example of Singleton in JavaScript:

class Singleton {
  constructor() {
    if (Singleton.instance) {
      return Singleton.instance;
    }
    this.value = Math.random();
    Singleton.instance = this;
  }
}

const a = new Singleton();
const b = new Singleton();
console.log(a === b); // true