Creational

Singleton

Type of object that can be instantiated once

In Typescript, just use a global object, so you don't have the boilerplate.

Prototype

Object.getPrototypeOf

Builder

Build object step by step through different methods instead of using many parameters

Factory

Determine which object to instantiate

Structural

Facade

Simplified to hide low-level details of a system

Proxy

Reactivity system of Vue :D

Replace an original object and do some side effects

Advantage: allow user to work with the proxy just like the original object but it can trigger side effects behind the scene.

Proxy are also used when there is a large object that would be expensive to duplicate in memory.

Behavioral

Iterator

Traverse through a collection of objects.

A pull based system.

An object with a next() method in javascript that returns a { done: boolean; value: T }.

Observer

Allow many objects to subscribe to events that are broadcast by another object.

A Subject where other objects subscribe to it and triggers their method when the subject notify

Mediator

In case of many to many relationships, one object is a coordinator between them.

Middlewares are an example of mediator.

State

What is the difference between state and strategy pattern?