Ali Shirani

Posted on May 28

10 Design Patterns Every Developer Should Know

#webdev #programming #beginners #productivity

Okay, this is going to be FUN! We're diving into the secret sauce that transforms code from a tangled mess into a work of art (or at least, something your colleagues won't curse you for). Get ready to level up your developer game!

From Play-Doh Snakes to Architectural Marvels: 10 Design Patterns You NEED to Know!

Ever feel like your early code resembled those colorful, slightly lumpy Play-Doh snakes we all proudly made as kids? You're not alone! We've all been there. Then, as you journey towards becoming a seasoned developer, you start hearing whispers of "design patterns." Suddenly, your code begins to take on the elegance and structure of the Sistine Chapel.

But here's a little secret from the trenches: sometimes, when you reach that principal engineer peak, you realize maintaining a digital Sistine Chapel for every simple website is... overkill. And you find a new appreciation for the elegant simplicity of well-crafted Play-Doh snakes.

The truth lies somewhere in between. Today, we're unlocking 10 essential software design patterns – powerful, battle-tested solutions to common problems you'll face every single day. We'll explore their pros, their cons (yes, they have them!), and when to whip them out of your coding toolkit.

This isn't just about memorizing syntax; it's about understanding how to solve problems effectively. Think of these patterns not as rigid rules, but as blueprints from the legendary "Gang of Four" (the authors of the seminal "Design Patterns" book) and beyond, categorized into:

Creational Patterns: How objects get made.
Structural Patterns: How objects connect and relate.
Behavioral Patterns: How objects talk to each other.

A Word of Caution: These patterns are like power tools. In the right hands, they build masterpieces. Used carelessly, they can add unnecessary complexity. The goal isn't to sprinkle them everywhere, but to recognize when they genuinely simplify and strengthen your code.

Alright, let's roll up our sleeves and get to it!

1. The Singleton Pattern: The "One Ring to Rule Them All"

The Gist: Ensures a class has only one instance and provides a global point of access to it. Think of it like the main settings object for your app – you only need one!
How it Works (Conceptually):
- The constructor is made private, so you can't just new it up willy-nilly.
- A static method (getInstance()) checks if an instance already exists. If yes, it returns it. If not, it creates one, stores it, and then returns it.
The Catch in JavaScript: JavaScript's object literals and module system often give you Singleton-like behavior out of the box. A simple global object or a module exporting an object can achieve the same thing with less boilerplate. > Key Takeaway: "Lean on your language's built-in features before implementing a fancy design pattern." – Wise words from the video!

2. The Prototype Pattern: The "Clone Machine"

The Gist: Creates new objects by copying an existing object (the prototype), rather than instantiating a new one from a class in the traditional sense. It's like cloning sheep!
Why Bother? It can be an alternative to complex class inheritance hierarchies, especially in dynamic languages. You create a base object, and then new objects "inherit" from it by being cloned and then customized.

In JavaScript: JavaScript has prototypal inheritance built-in! Object.create() is your friend here. You pass it the object you want to clone (the prototype), and it gives you a new object linked to the original.

// Super simplified concept
const zombiePrototype = {
    eatBrains: function() { console.log("Yummy brains!"); }
};

const steveTheZombie = Object.create(zombiePrototype);
steveTheZombie.name = "Steve";

steveTheZombie.eatBrains(); // Works!
console.log(steveTheZombie.name); // Steve

Interesting Tidbit: When you access a property on a JavaScript object, if it's not found, JavaScript walks up the "prototype chain" looking for it on its parent objects.

3. The Builder Pattern: The "Custom Sandwich Order"

The Gist: Separates the construction of a complex object from its representation, allowing you to create different variations of an object step-by-step. Think of ordering a custom Subway sandwich – you pick the bread, then the meat, then the veggies, one step at a time.
Problem Solved: Avoids constructors with a million parameters (telescoping constructors) and makes object creation more readable and flexible.

How it Looks: Often uses method chaining. Each method sets a part of the object and returns this (the instance itself), so you can chain the next call.

// Conceptual hotdog stand
class HotDog {
    constructor() { this.toppings = []; }
    addKetchup() { this.toppings.push('ketchup'); return this; }
    addMustard() { this.toppings.push('mustard'); return this; }
    addRelish() { this.toppings.push('relish'); return this; }
    serve() { console.log(`Serving hotdog with: ${this.toppings.join(', ')}`); return this; }
}

new HotDog().addKetchup().addMustard().serve();

Relevance: You've seen this in libraries like jQuery. While still useful, it's sometimes seen as a bit "last season" in modern JS, but the core idea of constructing objects step-by-step is timeless.

4. The Factory Pattern: The "Component Vending Machine"

The Gist: Instead of directly using the new keyword to create objects, you call a dedicated function or method (the "factory") to do it for you.
Why? It decouples your code from concrete classes. The factory can decide which specific type of object to create based on some logic (e.g., environment, user input).
Practical Example: Imagine a cross-platform app. You need a button. Instead of if (isIOS) new IOSButton() else new AndroidButton(), you have a ButtonFactory.createButton() that handles that logic internally.
Benefit: Makes your code more maintainable and easier to extend with new types of objects without changing the client code that uses the factory.

5. The Facade Pattern: The "Simple Remote Control"

The Gist (Structural): Provides a simplified, higher-level interface to a complex subsystem of components. It's like the clean, simple face of a building that hides all the messy plumbing, electrical, and structural shenanigans inside.
Problem Solved: Hides complexity. Makes a complex system easier to use by providing a "good enough" interface for most common tasks.
Analogy: Think of jQuery. It provided a much simpler way to interact with the often-clunky browser DOM APIs. You didn't need to know all the low-level details; jQuery gave you a friendly facade.
Key Idea: You're not preventing access to the underlying systems, just offering an easier entry point.

6. The Proxy Pattern: The "Bodyguard" or "Substitute"

The Gist (Structural): Provides a surrogate or placeholder for another object to control access to it. Like a substitute teacher filling in for the real one, or a bodyguard controlling who gets to see the VIP.
Why Use It?
- Lazy Loading: Only load a large object when it's actually needed.
- Access Control: Check permissions before allowing an operation.
- Logging/Caching: Intercept calls to add logging or cache results.
- Reactivity (like in Vue.js): When you change data on a proxy object, Vue's reactivity system can intercept that change (via get and set handlers) and update the UI.
In JavaScript: The Proxy object is a native feature, perfect for implementing this!

7. The Iterator Pattern: The "Guided Tour"

The Gist (Behavioral): Provides a way to access the elements of an aggregate object (like an array or list) sequentially without exposing its underlying representation. Think of a "Next" button on a music player.
Already Familiar: If you've used a for...of loop in JavaScript to go through an array, you've used the Iterator pattern!
Custom Iterators: You can create your own! For example, the video mentions creating a range iterator in JavaScript to iterate a certain number of times at a specific interval. This involves defining an object with a next() method that returns an object with value and done properties.
```
// Conceptual: How a for...of loop might work with an iterator
// const myArray = [1, 2, 3];
// for (const item of myArray) { /* ... */ }
// myArray must have a [Symbol.iterator]() method that returns an iterator object.
```
Core Idea: Separates the traversal logic from the collection itself. It's a "pull-based" system – you ask for the next item.

8. The Observer Pattern: The "News Subscription"

The Gist (Behavioral): Defines a one-to-many dependency between objects so that when one object (the "subject" or "publisher") changes state, all its dependents ("observers" or "subscribers") are notified and updated automatically.
Real-World Analogy: Subscribing to a YouTube channel. When the creator posts a new video (state change), all subscribers get a notification.
Use Cases: Event handling, UI updates (like Firebase data syncing to clients), reactive programming (RxJS is a prime example).
Key Idea: It's a "push-based" system. The subject pushes updates to its observers.

9. The Mediator Pattern: The "Air Traffic Controller"

The Gist (Behavioral): Defines an object (the "mediator") that encapsulates how a set of objects interact. Instead of objects talking directly to each other (a messy many-to-many web), they all talk to the mediator, which coordinates their actions.
Analogy: An air traffic controller. Airplanes don't talk directly to all other airplanes and runways; they communicate with the controller, who manages landings and takeoffs.
Problem Solved: Reduces coupling between objects. Makes it easier to change the interaction logic because it's centralized in the mediator.
Example: Express.js middleware. An incoming request (airplane) goes through middleware (the mediator system) which can transform it before it reaches its final handler (the runway).
Benefit: Promotes looser coupling and better separation of concerns.

10. The State Pattern: The "Mood Ring" Object

The Gist (Behavioral): Allows an object to alter its behavior when its internal state changes. The object will appear to change its class.
Problem Solved: Avoids massive if/else if/else or switch statements based on an object's state. Instead, you encapsulate state-specific behavior in separate "state" objects.
How it Works:
1. Define a base "state" interface/class.
2. Create concrete state classes that implement this interface, each with its own behavior for the methods.
3. The main object (the "context") holds a reference to a current state object.
4. When a method is called on the context, it delegates the call to its current state object.
5. The context or the state objects can transition the context to a new state.
Example: A Human object whose think() method behaves differently based on its mood (HappyState, SadState, AngryState). Instead of a switch statement in Human.think(), the Human object delegates to this.mood.think().
Benefit: Makes an object's behavior predictable and easier to manage as the number of states grows. Related to the concept of Finite State Machines (FSMs).

Beyond the Blueprints: Making Patterns Work for YOU

Phew! That was a whirlwind tour. Remember, these design patterns are tools, not commandments carved in stone. The real skill lies in:

Recognizing when a problem you're facing has a known pattern-based solution.
Understanding the trade-offs of applying a particular pattern.
Adapting the pattern to fit your specific context and programming language.

Becoming a proficient software engineer isn't just about knowing a language's syntax; it's about wielding these powerful problem-solving techniques to build robust, maintainable, and elegant software.

Now, over to you! Which of these design patterns do you find yourself using most often? Are there any others you think every developer should know? Share your thoughts in the comments below!

Top comments (1)

Sawyer Wolfe • Jun 4

Great breakdown of the main design patterns! Love the relatable examples for each one—makes them super easy to remember.