My Zero-Dep State Sync Lib: 5 Key Lessons for 2025 Devs
Discover 5 crucial lessons from building a zero-dependency state sync library. Learn about vanilla JS, API design, and future-proof dev for 2025.
Alex Ivanov
Principal Software Engineer specializing in performance, JavaScript architecture, and minimalist libraries.
Introduction: The Dependency Dilemma
In the world of modern web development, the node_modules
directory has become both a running joke and a genuine source of anxiety. We build applications on mountains of dependencies, each adding to our bundle size, increasing potential security vulnerabilities, and creating a complex web of abstractions that can be difficult to debug. State management, in particular, is a field rife with heavy, opinionated libraries that often lock you into a specific ecosystem.
Frustrated by this trend, I set out on a personal project: to build a lightweight, performant, and, most importantly, zero-dependency state synchronization library. The goal was simple: provide a robust way to keep state in sync across different parts of an application without pulling in a single third-party package. The journey was incredibly rewarding, and it taught me five crucial lessons that I believe will define successful software development in 2025 and beyond.
Lesson 1: Embrace the Platform (Vanilla is King)
The Siren Call of Dependencies
When you need reactivity, it's tempting to reach for Vue. When you need a component model, you think of React. But what if you just need reactivity? The modern web platform offers an incredibly powerful set of native tools that often go overlooked. Resisting the urge to npm install
was the first and most important rule of this project.
By committing to zero dependencies, I was forced to explore the full potential of vanilla JavaScript and TypeScript. This wasn't about reinventing the wheel; it was about realizing the platform already provides the high-quality rubber and steel you need to build your own, perfectly-sized wheel.
The Power of Native APIs
Two native APIs became the cornerstone of my library: Proxy
and CustomEvent
.
- Proxy Objects: The
Proxy
object allows you to create a wrapper around another object, intercepting fundamental operations like getting or setting properties. This is the secret sauce for creating truly reactive state objects without any external code. You can detect a change the moment it happens and trigger your synchronization logic. - Custom Events: For broadcasting state changes,
CustomEvent
is a beautifully simple and decoupled mechanism. Components don't need to know about a central store; they just need to listen for a specific event on a shared target (like thewindow
or a common DOM element). This makes the system incredibly portable and easy to integrate into any existing architecture.
The result? A core reactive system in under 50 lines of code, with no bundle size cost beyond my own logic. This is a stark contrast to the kilobytes (or megabytes) that a full-fledged framework adds for similar functionality.
Lesson 2: Simplicity Isn't Simple (The Art of API Design)
A zero-dependency library is only useful if its API is more straightforward than the problem it's solving. I spent more time refining the public API than I did on the internal implementation. True simplicity isn't about having the fewest lines of code; it's about creating an interface that is intuitive, predictable, and requires minimal cognitive load from the developer using it.
Designing for Intuition
My first few attempts involved complex configuration objects and multi-step setups. It was powerful but clunky. The breakthrough came when I focused on a developer's intent. What do they want to do? They want to create a shared state and then use it. The final API reflects this directness:
const myState = createSharedState({ count: 0 });
myState.subscribe(newState => console.log(newState.count));
myState.update(currentState => ({ count: currentState.count + 1 }));
This API is clean, declarative, and easy to understand. Getting to this point required abstracting away all the internal complexity of Proxies, event listeners, and update batching (more on that next). The lesson here is to obsess over the developer experience. A simple API is a feature, and it's one of the hardest to build.
Lesson 3: Performance is a Feature, Not an Afterthought
When you have a reactive system, it's easy to create performance bottlenecks. If every single state mutation immediately triggers a UI update, you can quickly cause layout thrashing, where the browser is forced to recalculate styles and layout repeatedly. Performance can't be bolted on at the end; it must be designed in from the start.
Batching Updates with Microtasks
The key to high-performance state sync is to decouple the state change from the notification. When the state is updated, instead of immediately telling all the subscribers, I schedule the notification to run in a microtask using queueMicrotask()
.
This is a game-changer. If you have multiple state updates in the same synchronous block of code (e.g., inside a loop or a single function), they will all be queued. The notification to subscribers will only fire once at the end of the current task, containing the final, fully updated state. This ensures that the UI (or any other listener) only re-renders once, dramatically improving performance.
Feature | Direct DOM Manipulation | Virtual DOM (e.g., React) | My Lib's Batched Sync |
---|---|---|---|
Performance | Fast for simple cases, slow with many updates | Efficiently diffs and updates | Highly performant, avoids thrashing |
Complexity | Low initially, high to manage at scale | High, requires framework knowledge | Low, abstracted away from the user |
Bundle Size | Zero | Medium to Large (framework cost) | Tiny (<1KB gzipped) |
Best For | Small scripts, simple interactions | Complex single-page applications | Lightweight apps & framework-agnostic components |
Lesson 4: The Future is Interoperable (Framework Agnostic)
The JavaScript landscape is constantly shifting. A library tightly coupled to React today might be irrelevant in a world dominated by Svelte, Qwik, or something that hasn't even been invented yet. Building a zero-dependency library inherently makes it framework-agnostic.
Breaking Out of the Silo
My state library can be imported and used in a React component, a Vue composable, a Svelte store, an Angular service, or a vanilla JS Web Component with equal ease. It doesn't impose any structure or opinions on your application. This level of interoperability is a superpower. It's crucial for:
- Micro-frontends: Where different parts of your UI might be built with different technologies.
- Design Systems: Create a core set of business logic or state that can be consumed by component libraries for any framework.
- Longevity: Your logic remains valuable and portable even if you decide to migrate your application from one framework to another.
In 2025, developers will increasingly value tools that solve a specific problem well and get out of the way, rather than all-in-one solutions that dictate your entire architecture.
Lesson 5: Documentation is Your Most Important Dependency
You can have the most elegant, performant, zero-dependency code in the world, but if no one understands how to use it, it's worthless. For a small library, documentation isn't just a part of the project; it is the project.
More Than Just API Docs
Good documentation goes beyond a simple API reference. It needs to be a comprehensive guide that includes:
- The "Why": Explain the design decisions. Why zero dependencies? Why microtask batching? This builds trust and helps users understand the library's philosophy.
- Recipes & Patterns: Show, don't just tell. Provide clear, copy-pasteable examples for common use cases, like integrating with React Hooks or creating a derived store.
- Live Examples: Use platforms like CodePen or StackBlitz to create interactive, editable demos. This is the fastest way for a developer to try out your library and see its value.
I treated the README and documentation site as the primary user interface of the library. This focus on education and usability is the single most important factor in driving adoption for any open-source project.
Conclusion: Building for Tomorrow
Creating a zero-dependency state sync library was a powerful reminder that the web platform is more capable than we often give it credit for. The process reinforced that the future of development isn't about finding the one perfect framework, but about assembling small, focused, and interoperable tools. The five key lessons—embracing the platform, obsessing over API design, engineering for performance, ensuring interoperability, and treating documentation as a product—are not just for library authors. They are essential principles for any developer looking to build resilient, efficient, and future-proof applications in 2025 and beyond.