Immer and Immutable.js: How do they compare?

Immutability in programming, a concept that prevents direct changes to data post-creation, is fundamental to certain paradigms like pure functional programming and is evident in JavaScript, where primitives such as strings and numbers are immutable. However, JavaScript also supports mutable data structures like arrays. To address the need for immutability in JavaScript applications, particularly in frameworks like React, libraries like Immer and Immutable.js are utilized. Immer operates using a copy-on-write mechanism, allowing developers to work with familiar JavaScript data types while maintaining immutability, whereas Immutable.js provides an API for non-native JavaScript data structures like ordered maps and records, offering faster data writing but demanding new syntax knowledge. While both libraries serve to optimize applications and facilitate change tracking, Immer is favored for its flexibility and simplicity, whereas Immutable.js is chosen for its speed in writing operations. Each library has its own set of benefits and trade-offs, such as Immer's requirement for proxy-supporting environments and Immutable.js's slower read operations and need for unique construction types.