MSW 2.0: Embracing the Fetch API and Unlocking New Possibilities
October 23, 2023
Mock Service Worker (MSW) has come a long way since its inception five years ago. With the release of version 2.0, MSW has undergone significant changes, introducing a refined public API and first-class support for Fetch API primitives. In this blog post, we will explore the motivations behind these changes, the challenges faced during development, and the exciting possibilities that MSW 2.0 brings to the table.
The Evolution of MSW
Artem Zakharchenko, the maintainer of MSW, recognized the need for a change. He wanted developers to not only achieve their goals but also learn concepts and APIs that could be applied beyond MSW. With this in mind, version 2.0 of MSW was developed.
The Power of Fetch API
With the adoption of the Fetch API, MSW 2.0 introduces a new API for declaring request handlers and response resolvers. Now, both the request and response are instances of the Fetch API, providing a feature-rich and standardized way of handling requests and defining responses.
This change opens up a world of possibilities. Developers can now leverage the full power of the Fetch API, including features like reading the intercepted request’s body as FormData. MSW no longer relies on polyfills or custom representations of requests and responses, making the library more future-proof and compatible with different environments and tools.
Breaking Changes and Improvements
MSW 2.0 brings not only the adoption of the Fetch API but also numerous bug fixes and improvements. The library now has full compatibility with ESM, proper code splitting, improved internal architecture, and a refined interception algorithm in Node.js.
While these changes are exciting, they also come with breaking changes to the public API. However, the benefits of adopting the new API far outweigh the migration effort. Detailed migration guidelines are provided to help developers address each breaking change relevant to their setup.
Artem Zakharchenko’s dream is to work on MSW full-time and continue improving and evolving the library. To support this dream, he encourages developers to sponsor the project. Every contribution brings him a step closer to making this dream a reality.
With the incredible contributions from the community and the dedication of Artem Zakharchenko, MSW continues to evolve and improve. The future of MSW looks bright, and developers can expect even more exciting features and enhancements in the coming years.
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Introducing MSW 2.0