immutability

Return new object and array copies for immutable JavaScript state updates.

13|2|Updated Jan 21, 2026

Search Tags:#typescript #react #javascript #state-management #immutability #spread-operator

Ready to run

npx skills add https://github.com/yanko-belov/code-craft --skill immutability

💬 Prompt for ChatGPT / Claude Chat▼

Please help me install this Agent Skill.
Skill: immutability
Source: https://github.com/yanko-belov/code-craft/tree/main/skills/immutability
Command: npx skills add https://github.com/yanko-belov/code-craft --skill immutability

SYSTEM DOCUMENTATION & REQUIREMENTS

What problem does it solve?

Mutating objects or arrays can introduce subtle bugs and hard-to-track state changes. This Skill enforces immutability by always returning new copies instead of mutating existing data.

Core Features & Use Cases

Immutable updates: Replace objects or arrays with new copies to preserve original state.
Predictable state management: Improves debugging, undo/redo, and React change detection.
Use case: In a Redux-like app, when updating a user profile, return a new user object rather than mutating the existing one.

Quick Start

Use an immutable update pattern to modify an object, for example: return { ...obj, updated: true } instead of mutating obj.

Frequently Asked Questions about immutability

High-intent search queries and answers about installing and using this skill.

FAQPage Schema

How do I update JavaScript objects without mutating the original state?▼

To update JavaScript objects without mutating state, use the spread operator to return a new copy, such as `{ ...obj, updated: true }`. This preserves the original object and prevents unintended side effects in your code.

Why does React require immutable state updates for arrays and objects?▼

React requires immutable state updates because returning new objects allows its change detection system to identify updates quickly. Mutating existing arrays or objects directly can cause subtle bugs and prevent the UI from re-rendering properly.

What is the best way to manage state immutability in TypeScript applications?▼

The best way to manage state immutability in TypeScript is to adopt immutable patterns like spread syntax and array copies instead of relying on external tools. Always return new objects during updates to ensure predictable state management and easier debugging.

How do I add or remove items from an array without mutation in JavaScript?▼

To modify arrays without mutation in JavaScript, use spread syntax to create a new array copy. For example, use `[...arr, newItem]` to add elements, ensuring the original array remains unchanged and state updates remain predictable.

Do I need external libraries to enforce immutability in a Redux-like app?▼

No, you do not need external libraries to enforce immutability in a Redux-like app. You can prevent unintended state mutations by adopting immutable patterns natively, using spread syntax and object copies to return new instances during updates.

When should I avoid mutating objects in JavaScript state management?▼

You should avoid mutating objects in JavaScript state management whenever you need predictable state changes, undo/redo functionality, or reliable React change detection. Mutating data directly introduces hard-to-track bugs and complicates debugging processes.