JavaScript runtimes are evolving beyond Node.js, offering developers new tools designed for modern workflows, performance, and security. Two of the most talked-about options today are Deno and Bun. Both aim to improve the developer experience in different ways, bringing unique strengths and trade-offs. In this article, we’ll take a practical look at what they offer, how they differ, and when you might want to use one over the other.
Origins and Background
Deno
Deno was created by Ryan Dahl, the original developer of Node.js. After years of Node.js dominating the JavaScript ecosystem, Dahl identified several shortcomings around security, dependency management, and TypeScript support. Deno was designed to address these issues.
Bun
Bun was created by Jarred Sumner with a focus on performance and ease of use. Built with speed as its primary goal, Bun targets developers who want a faster, smoother experience.
Performance Comparison
Bun’s Speed
Bun is recognized for its speed, being written in Zig and using JavaScriptCore, the engine behind Safari. Key performance highlights include:
- Cold start times: Bun starts faster than both Deno and Node.js, ideal for CLI tools.
- HTTP servers: Benchmarks show Bun serving HTTP requests with lower latency and higher throughput.
- Package installation: Bun’s built-in package manager is faster than npm or pnpm, making dependency setup almost instant.
Deno’s Balanced Performance
Deno, built with Rust and using V8, focuses on predictable, reliable performance. It’s well-suited for:
- Long-running processes: Consistent memory usage makes it ideal for servers or APIs.
- Real-world workloads: Performs well under typical conditions like handling API requests or running TypeScript-heavy applications.
Language Support and TypeScript
Deno’s Native TypeScript Support
Deno offers native TypeScript support, allowing you to run .ts files directly without requiring separate tools. This integration simplifies workflows and treats TypeScript as a first-class citizen.
Bun’s Approach to TypeScript
Bun supports TypeScript by transpiling it to JavaScript using its own optimized implementation. However, it does not perform type-checking natively, requiring external tools like the TypeScript compiler (tsc) for strict type-checking.
Package Management Approaches
Deno’s URL-Based Imports
Deno uses URL-based imports, removing the need for a node_modules directory and ensuring every dependency is explicitly defined. Deno also supports npm compatibility, enabling the use of Node.js packages.
Bun’s Npm-First Model
Bun fully embraces the npm ecosystem with a built-in package manager designed to be faster than npm or pnpm. This makes Bun an excellent choice for projects relying heavily on existing Node.js libraries.
Security Features and Models
Deno’s Permissions Model
Deno’s strict permissions model requires explicit permission for file system access, network requests, and environment variables. This minimizes risks by ensuring code can only interact with the system in approved ways.
Bun’s Permissive Approach
Bun takes a more traditional approach, similar to Node.js, with no default restrictions on system resource access. This makes it easier to get started but leaves security entirely in the hands of the developer.
Development Tooling
Deno’s Built-In Tools
Deno offers several built-in features, including a test runner, formatter, linter, and task runner. These tools follow Deno’s philosophy of minimalism and standards compliance.
Bun’s Performance-Focused Tools
Bun provides built-in tools emphasizing speed, including a test runner, bundler, and package manager. These tools excel in performance, making Bun attractive for tasks like testing, bundling, and dependency installation.
Node.js Compatibility Layer
Deno’s Growing Compatibility
Deno has introduced features to support Node.js projects, including npm support and key Node.js APIs. However, some edge cases may still require additional effort.
Bun as a Drop-In Replacement
Bun aims to be a near-drop-in replacement for Node.js, with excellent npm compatibility and support for almost all Node.js APIs out of the box.
Developer Experience and Workflow
Ease of Use
- Deno: Focuses on clarity and standards, with a permissions model and URL-based imports enforcing best practices.
- Bun: Prioritizes familiarity and speed, feeling like a performance-enhanced version of Node.js.
Documentation and Resources
- Deno: Extensive official documentation and strong community support.
- Bun: Clear documentation and growing community, leveraging existing Node.js resources.
Ideal Use Cases
When to Choose Deno
- TypeScript-first projects
- Secure applications
- Modern API development
- CLI tools
When to Choose Bun
- Performance-critical applications
- Node.js migrations
- Prototyping and development
- Web applications
Comparison Table
| Feature | Deno | Bun |
|---|---|---|
| Philosophy | Secure-by-default, standards-compliant | Performance-focused, npm-centric |
| Primary Language | Rust, V8 JavaScript engine | Zig, JavaScriptCore engine |
| TypeScript Support | Native support; no configuration needed | Transpiles TypeScript; external type-checking |
| Module System | URL-based imports; supports npm packages | Integrated with npm; uses node_modules |
| Performance | Balanced performance in various tasks | Optimized for speed, especially in server tasks |
| Security | Explicit permissions model | No default restrictions |
| Node.js Compatibility | Growing support with npm integration | High compatibility; near drop-in replacement |
| Tooling and Packages | Runtime, bundler, test runner, formatter, linter | Runtime, bundler, test runner, package manager |
| Community and Maturity | Established, standards-driven | Emerging, rapidly growing |
Conclusion
Deno and Bun are both impressive JavaScript runtimes, each serving different purposes and catering to different priorities. The right runtime depends on your use case. If you’re building a secure backend API or a TypeScript-heavy CLI tool, Deno is hard to beat. If you’re looking for raw speed or want to stay close to the Node.js ecosystem, Bun is an excellent option.
JavaScript is evolving, and both Deno and Bun reflect the direction it’s heading. While they take different paths, they both push the boundaries of what developers can expect from modern runtimes.
For more information, check out the official documentation for Deno and Bun.