Applying Patterns in Modern TypeScript Projects

Design patterns can sometimes feel like a chapter ripped from a dusty programming textbook. Creational, structural, behavioral—those words echo like theory-heavy lectures. But when you’re knee-deep in a Next.js app or wiring up Nest.js modules, these patterns aren’t abstract at all. They’re everywhere. The trick is noticing them, knowing when to apply them, and—just as importantly—knowing when not to.

Patterns in the Wild: Nest.js, Next.js, Angular

Take Nest.js. At its core, the framework leans heavily on the Dependency Injection pattern. Services aren’t manually stitched together; they’re injected where needed. That’s a textbook creational pattern right there, but Nest makes it feel natural—almost invisible.

Or think about Next.js. Every time you configure middleware, wrap pages with higher-order components, or decorate API handlers, you’re brushing up against structural patterns. Angular takes it even further, embedding patterns like Observer (via RxJS) into its DNA. If you’ve used Angular’s async pipe or subscribed to a form’s value changes, congratulations—you’ve already been wielding a behavioral pattern without necessarily labeling it.

When Patterns Show Up Naturally

The interesting thing is, most developers stumble into patterns before they ever read about them. You create a wrapper function around an API because the old interface is clunky? That’s an Adapter. You centralize business rules into swappable strategies? You’ve just implemented Strategy. Patterns are less about forcing architecture and more about giving names to the things we intuitively build.

Here’s the thing: once you recognize the names, communication gets easier. Saying “let’s add a decorator for that service” is a lot faster than explaining “we’ll wrap the class and extend behavior without modifying it.” Patterns turn vague architectural conversations into clear, precise collaboration.

Recognizing When Not to Use a Pattern

But let’s be real—sometimes developers go overboard. Ever seen a codebase where someone force-fit every Gang of Four pattern just to show they could? The result is usually overengineered spaghetti that nobody wants to maintain.

Not every problem needs a pattern. A simple if statement can beat a full-blown Strategy implementation if the logic is straightforward. A function closure might be cleaner than building a full Command pattern. Patterns are tools, not laws. Reaching for them when they’re unnecessary is like using a Swiss Army knife to butter toast—it works, but it feels ridiculous.

Breathing New Life into Legacy JavaScript

Now here’s where patterns really shine: refactoring legacy code. If you’ve ever opened a ten-year-old JavaScript file with thousands of lines and no clear structure, you know the dread. Modern TypeScript plus patterns can turn that chaos into something maintainable.

For example:

• Wrap a gnarly callback-based API with the Adapter pattern, exposing a clean Promise-based interface.
• Introduce Strategy to handle different business rules that were previously tangled in giant switch statements.
• Use Observer (via RxJS) to tame event handling chaos.

Patterns become a bridge—not just to cleaner code, but to a mindset shift. They help teams speak a common language while modernizing what came before.

A Handy Cheat Sheet: Creational, Structural, Behavioral

To wrap it up, here’s a quick summary that connects the dots:

• Creational Patterns → focus on object creation
  (Factory, Singleton, Builder)
• Structural Patterns → deal with composition and relationships
  (Adapter, Decorator, Proxy)
• Behavioral Patterns → manage communication and responsibility
  (Observer, Strategy, Command)

You don’t need to memorize every variant. What matters is knowing the categories and recognizing when a solution naturally aligns with one of them.

Final Thoughts

TypeScript and modern frameworks make patterns feel less like academic jargon and more like second nature. You’ve probably been using them already, even if you didn’t call them by name. The challenge isn’t applying every pattern you know—it’s developing the judgment to pick the right one, at the right moment, for the right reason.

And if nothing else, having “patterns in your back pocket” gives you a shortcut in conversations. Because let’s be honest: telling your team you “refactored a legacy module into Strategy-based components” just sounds better than “I broke up a giant if-else chain.”