Mutative

Mutative is a JavaScript library designed for performing efficient immutable updates on data structures, drawing inspiration from libraries like Immer but with a strong focus on performance. It allows developers to write 'mutative' logic inside a producer function, and Mutative handles the underlying copy-on-write mechanism to return a new, immutably updated state. The library is currently at version 1.3.0 and exhibits an active release cadence, with frequent patch and minor updates. Key differentiators include its reported performance benefits, claiming to be 2-6x faster than naive handcrafted reducers using spread operators and over 10x faster than Immer, primarily through shallow copy optimization, lazy drafts, and an optimized finalization process. It aims to address issues like Immer's mandatory auto-freeze and improve type inference and handling of various immutability edge cases.