kitten/hachiko

Hachiko is a JavaScript library designed to provide modular and performant data collections, offering an alternative to Immutable.js with a similar API but a smaller focus and micro optimizations. It is particularly useful for developers seeking persistent data structures like Map, List, OrderedMap, Set, and OrderedSet, with enhanced performance in common benchmarks. However, development has been abandoned, with only the Map data structure fully implemented as of December 2016.