Create immutable JavaScript states by writing mutable code, simplifying state management in React and beyond.
Immer is a JavaScript library that simplifies working with immutable state by allowing developers to write code that appears to mutate objects directly. It automatically produces a new immutable state tree from the modifications, eliminating the need for manual deep copying or spread operators. This makes state updates more intuitive and less error-prone, especially in complex applications.
Frontend developers working with state-heavy applications in React, Redux, or other frameworks where immutable updates are required. It's particularly valuable for teams dealing with deeply nested state structures.
Developers choose Immer because it dramatically reduces boilerplate code for immutable updates while maintaining performance through structural sharing. Its intuitive mutable-like API lowers the cognitive load compared to traditional immutable patterns, making state management more accessible without sacrificing correctness.
Create the next immutable state by mutating the current one
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Allows writing state updates as if mutating objects directly, eliminating the need for manual spread operators or deep copies, as described in the key features for a mutable API.
Only copies the parts of the state that change, reducing memory usage and improving performance, which is highlighted in the structural sharing feature.
Provides full TypeScript support with excellent type inference, making development smoother and type-safe, as noted in the TypeScript support feature.
With a bundle size around 3KB gzipped and zero dependencies, it adds minimal overhead to projects, as emphasized in the tiny footprint feature.
Relies on JavaScript Proxies, which are not supported in all environments (e.g., IE11), potentially requiring polyfills or limiting compatibility in older systems.
For very large or complex state trees, the proxy-based approach can introduce performance bottlenecks compared to manual immutable updates, though structural sharing mitigates this.
Since Immer abstracts away the immutability, debugging state changes might require understanding its internal proxy mechanisms, which can be non-trivial for beginners.