Immer: A Solution for Immutability in JavaScript

 Immutability is a fundamental concept in functional programming. It ensures that data remains unchanged, or immutable, as it travels through your code. However, achieving immutability in JavaScript can be tricky. This is where Immer comes in.

What is Immer?

Immer is a tiny package that allows you to work with immutable state in a more convenient way. It is based on the copy-on-write mechanism. The name ‘Immer’ is a German word for ‘always’, signifying that your data is always safe and unaltered.

Why Immer?

Immer uses a different approach to achieve immutability. It allows you to write code in a mutable manner, but behind the scenes, it applies all the changes to a draft state, which results in a new immutable state.

How does Immer work?

Immer works by using a produce function. This function takes two parameters: the current state and a function that defines how the state should be updated. Here’s a simple example:

import produce from "immer";

let state = { value: 1 };

let nextState = produce(state, draftState => {

    draftState.value = 2;


console.log(nextState.value); // Output: 2

In the above code, state remains unaltered, while nextState is a new object reflecting the changes.

Benefits of Immer

  1. Simplicity: Immer lets you write simpler and cleaner code by abstracting the complexities of immutability.

  2. Efficiency: Immer only copies the parts of the state that were changed, making it more efficient than deep cloning.

  3. Compatibility: Immer is compatible with any JavaScript application or library.


Immer provides a robust and efficient solution for managing immutable state in JavaScript applications. It simplifies the process of updating state, making your code easier to write and understand.

Remember, immutability might seem like an overhead initially, but it brings long-term benefits to the maintainability and predictability of your code.

Happy coding!

Please note that this is a draft and may require further editing and proofreading.