react18-lifecycle-patterns
Provides exact before/after migration patterns for the three unsafe class component lifecycle methods - componentWillMount, componentWillReceiveProps, and componentWillUpdate - targeting React 18.3.1. Use this skill whenever a class component needs its lifecycle methods migrated, when deciding between getDerivedStateFromProps vs componentDidUpdate, when adding getSnapshotBeforeUpdate, or when fixing React 18 UNSAFE lifecycle warnings. Always use this skill before writing any lifecycle migration code - do not guess the pattern from memory, the decision trees here prevent the most common migration mistakes.
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Install
Works with every agent the skills CLI supports.
npx skills add https://github.com/github/awesome-copilot --skill react18-lifecycle-patterns- 01
Install
Run the command in your project. The CLI asks which agents to install for.
- 02
Describe the task
Ask your agent for something this skill covers. It loads react18-lifecycle-patterns automatically when relevant.
- 03
Review the result
The agent follows the SKILL.md steps, scripts and references bundled with the skill.
SKILL.md
The instructions your agent reads when the skill is triggered.
React 18 Lifecycle Patterns
Reference for migrating the three unsafe class component lifecycle methods to React 18.3.1 compliant patterns.
Quick Decision Guide
Before migrating any lifecycle method, identify the semantic category of what the method does. Wrong category = wrong migration. The table below routes you to the correct reference file.
componentWillMount - what does it do?
| What it does | Correct migration | Reference |
|---|---|---|
Sets initial state (this.setState(...)) | Move to constructor | → componentWillMount.md |
| Runs a side effect (fetch, subscription, DOM) | Move to componentDidMount | → componentWillMount.md |
| Derives initial state from props | Move to constructor with props | → componentWillMount.md |
componentWillReceiveProps - what does it do?
| What it does | Correct migration | Reference |
|---|---|---|
| Async side effect triggered by prop change (fetch, cancel) | componentDidUpdate | → componentWillReceiveProps.md |
| Pure state derivation from new props (no side effects) | getDerivedStateFromProps | → componentWillReceiveProps.md |
componentWillUpdate - what does it do?
| What it does | Correct migration | Reference |
|---|---|---|
| Reads the DOM before update (scroll, size, position) | getSnapshotBeforeUpdate | → componentWillUpdate.md |
| Cancels requests / runs effects before update | componentDidUpdate with prev comparison | → componentWillUpdate.md |
The UNSAFE_ Prefix Rule
Never use UNSAFE_componentWillMount, UNSAFE_componentWillReceiveProps, or UNSAFE_componentWillUpdate as a permanent fix.
Prefixing suppresses the React 18.3.1 warning but does NOT:
- Fix concurrent mode safety issues
- Prepare the codebase for React 19 (where these are removed, with or without the prefix)
- Fix the underlying semantic problem the migration is meant to address
The UNSAFE_ prefix is only appropriate as a temporary hold while scheduling the real migration sprint. Mark any UNSAFE_ prefix additions with:
// TODO: React 19 will remove this. Migrate before React 19 upgrade.
// UNSAFE_ prefix added temporarily - replace with componentDidMount / getDerivedStateFromProps / etc.
Reference Files
Read the full reference file for the lifecycle method you are migrating:
references/componentWillMount.md- 3 cases with full before/after codereferences/componentWillReceiveProps.md- getDerivedStateFromProps trap warnings, full examplesreferences/componentWillUpdate.md- getSnapshotBeforeUpdate + componentDidUpdate pairing
Read the relevant file before writing any migration code.
FAQ
What does the react18-lifecycle-patterns skill do?
Provides exact before/after migration patterns for the three unsafe class component lifecycle methods - componentWillMount, componentWillReceiveProps, and componentWillUpdate - targeting React 18.3.1. Use this skill whenever a class component needs its lifecycle methods migrated, when deciding between getDerivedStateFromProps vs componentDidUpdate, when adding getSnapshotBeforeUpdate, or when fixing React 18 UNSAFE lifecycle warnings. Always use this skill before writing any lifecycle migration code - do not guess the pattern from memory, the decision trees here prevent the most common migration mistakes.
How do I install react18-lifecycle-patterns?
Run npx skills add https://github.com/github/awesome-copilot --skill react18-lifecycle-patterns in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/react18-lifecycle-patterns/ (personal) or .claude/skills/react18-lifecycle-patterns/ (project).
Which AI agents can use react18-lifecycle-patterns?
Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.
Is react18-lifecycle-patterns safe to install?
No partner security audit is available yet. Skills can run commands and scripts, so read the SKILL.md and any bundled files before installing.
Who maintains react18-lifecycle-patterns?
It is published by github in github/awesome-copilot, and it is an official skill from the maker of the technology it covers. It has 743 recorded installs.
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