Design patterns in Node.js are essential solutions to common software design issues faced while designing apps. They offer reusable templates for structuring code, and improving maintainability, scalability, and readability in Node.js applications.
The Singleton pattern ensures that only one instance of a class is created and available throughout the program. In Node.js, this pattern ensures that a module has just one instance.
The Factory pattern is used to generate objects without exposing their creation logic to the client. In Node.js, this pattern is used to generate instances of various classes based on the input.
The Observer pattern is used to keep track of a list of dependents who should be notified when the object being monitored changes. In Node.js, this pattern is used to handle events and callbacks.
Passing dependencies into a component from the outside rather than creating them within the component promotes loose coupling and makes testing and modularization easier in Node.js applications.
The Promise Pattern expresses the eventual completion or failure of an asynchronous activity, providing for a more understandable and controlled asynchronous code flow in Node.js. It is especially useful for dealing with asynchronous operations like as file I/O or network requests.
Node.js defaults to using the module pattern to organize code into reusable and manageable modules. Node.js treats each file as a module, and developers can use the "require" and "module.exports" directives to export and import code between files.
Node.js handles I/O operations using an event-driven approach, such as reading and writing data to files or network sockets. The event-driven design builds on the Observer pattern, allowing developers to create event emitters that can alert listeners when specific events occur.
Asynchronous actions, such as reading and writing files or making network queries, are handled by Node.js using the callback pattern. The callback pattern is based on the Observer pattern and allows developers to give functions as parameters that will be performed when an operation is completed.
Middleware is a design pattern that is frequently used in Node.js frameworks such as Express. Middleware functions are pipelined functions that can modify request or response objects before delivering them to the next function.