rxjs vs mitt

utility

rxjs

mitt

RxJS is a comprehensive reactive programming library that implements the Observable pattern for composing asynchronous and event-based programs using observable sequences. It provides a vast collection of operators (over 100) for transforming, filtering, combining, and managing streams of data over time. Mitt, on the other hand, is a minimal 200-byte event emitter library that provides a simple publish-subscribe pattern for decoupled communication between components.

This comparison is relevant because developers often evaluate these libraries when they need event handling or reactive programming capabilities, but the two tools operate at vastly different scales and complexity levels. RxJS targets developers building complex data flow applications with requirements like backpressure handling, sophisticated stream transformations, and coordinated async operations. Mitt appeals to developers who need straightforward event communication without the overhead of a full reactive programming paradigm, particularly in small to medium-sized applications or library development where bundle size is critical.

Head-to-Head

Bundle Size→ mitt wins

rxjs

RxJS weighs approximately 30-50KB minified (depending on tree-shaking), making it a substantial addition to your bundle. Even with careful imports of specific operators, you'll typically include 15-20KB minimum for basic usage.

mitt

Mitt is extraordinarily lightweight at 200 bytes minified and gzipped. The entire library is smaller than a single RxJS operator, making it negligible in bundle size impact and ideal for performance-sensitive or library contexts.

API Complexity→ mitt wins

rxjs

RxJS has a steep learning curve with extensive APIs including creation operators (of, from, interval), transformation operators (map, mergeMap, switchMap), filtering operators, and combination operators. Understanding concepts like hot vs cold observables, subjects, schedulers, and operator chaining requires significant investment.

mitt

Mitt exposes only three methods: on(), off(), and emit(). The entire API can be learned in minutes with a standard event emitter pattern familiar to most JavaScript developers. No special concepts or patterns required beyond basic pub-sub.

Stream Composition Capabilities→ rxjs wins

rxjs

RxJS excels at composing complex asynchronous operations with operators like debounceTime, retry, combineLatest, and switchMap. You can easily handle scenarios like canceling previous requests, combining multiple streams, or implementing sophisticated retry logic with exponential backoff.

mitt

Mitt has no stream composition capabilities. It's a simple event emitter where listeners receive events independently. You cannot chain transformations, combine multiple event sources, or apply temporal operators without writing custom logic.

TypeScript Supporttie

rxjs

RxJS has excellent TypeScript support with complete type definitions, generic types that flow through operator chains, and type inference that catches many errors at compile time. The types accurately represent the transformation of values through observable pipelines.

mitt

Mitt has good TypeScript support with type definitions and the ability to type event names and payloads. However, the type system is simpler, providing basic type safety for event names and handler arguments without complex generic transformations.

Memory Management→ mitt wins

rxjs

RxJS requires careful subscription management to prevent memory leaks. You must explicitly unsubscribe from observables or use operators like takeUntil to manage subscription lifecycles. Forgetting to unsubscribe is a common source of memory leaks in RxJS applications.

mitt

Mitt also requires manual cleanup by calling off() to remove listeners, but the simpler model means fewer opportunities for complex memory leak scenarios. The straightforward API makes it easier to track and manage listener registrations.

Async Operation Handling→ rxjs wins

rxjs

RxJS is purpose-built for async operations with native support for cancellation, retry logic, error handling strategies, and coordinating multiple async sources. Features like switchMap automatically cancel previous async operations when new values arrive.

mitt

Mitt has no built-in async operation handling. It simply fires events synchronously to registered listeners. If you need to handle promises, cancellation, or async coordination, you must implement this logic yourself in the event handlers.

Verdict

Choose Mitt when you need simple event communication between components or modules and bundle size matters. It's perfect for libraries, small applications, or any scenario where the traditional event emitter pattern suffices. If you're building a widget, UI component library, or application where events represent discrete occurrences without complex transformations, Mitt provides everything you need without bloat. The simplicity also means easier onboarding for team members and fewer potential bugs from complex reactive logic.

Choose RxJS when you're dealing with complex asynchronous data flows, need stream composition, or require sophisticated handling of events over time. If your application involves coordinating multiple API calls, implementing autocomplete with debouncing and cancellation, managing WebSocket streams, or handling complex user interaction sequences, RxJS's operator library will save you from reinventing these patterns. The bundle size cost is justified when you actually need reactive programming capabilities—using RxJS just for basic events is overkill and unnecessarily increases complexity.

When to Use Each

If you are building a small UI component library that needs event communication between components → use Mitt because the 200-byte footprint won't burden your users and the simple API is sufficient for component event delegation.

If you are implementing a real-time dashboard that combines WebSocket data, polls multiple APIs, and needs to handle user input with debouncing → use RxJS because you need stream composition, operators like combineLatest and debounceTime, and the ability to manage multiple async sources declaratively.

If you are creating a plugin system where plugins emit lifecycle events and the host application listens to them → use Mitt because you need straightforward publish-subscribe without async complexity, and the minimal footprint is ideal for extensibility scenarios.

If you are building a search feature that needs to cancel previous API requests when users type, debounce input, and retry failed requests → use RxJS because switchMap handles cancellation automatically, debounceTime manages input timing, and retry operators handle failure scenarios without custom logic.

Learn More

rxjs →mitt →

Head-to-Head

Bundle Size→ mitt wins

rxjs

mitt

API Complexity→ mitt wins

rxjs

mitt

Stream Composition Capabilities→ rxjs wins

rxjs

mitt

TypeScript Supporttie

rxjs

mitt

Memory Management→ mitt wins

rxjs

mitt

Async Operation Handling→ rxjs wins

rxjs

mitt

Verdict

When to Use Each