# jscodeshift

A rule set for writing and debugging jscodeshift codemods: AST traversal, code migrations, automated refactoring.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 410 installs · ★ 218
- Author: pproenca
- License: MIT · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/pproenca/dot-skills/tree/HEAD/skills/.experimental/jscodeshift/SKILL.md
- Updated: 2026-08-15
- HTML: https://affpapa.org/en/nevibecode/skills/jscodeshift

## What it does

This skill packs the jscodeshift codemod practices used at Facebook/Meta. It holds 40 rules across 8 categories, ordered by impact from parser configuration and AST traversal down to advanced patterns. Each rule ships with an explanation, examples and impact notes.

Categories carry prefixes: `parser-`, `traverse-`, `filter-`, `transform-`, `codegen-`, `test-`, `runner-`, `advanced-`. Parser setup and traversal patterns sit at the top because a mistake there breaks the whole transform. Node filtering, transformation, code generation, testing and runner tuning follow.

Rules live as separate files under `references/`, with a template for adding new ones and a compiled guide in `AGENTS.md`. Reach for it when a transform blows up on unexpected syntax or a run over a large codebase needs to go faster.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add pproenca/dot-skills --skill jscodeshift -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/jscodeshift/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/jscodeshift/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add pproenca/dot-skills --skill jscodeshift -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/jscodeshift/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add pproenca/dot-skills --skill jscodeshift -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/jscodeshift/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install pproenca/dot-skills jscodeshift
```

2. **Manually: put the files in place**
- File: `.github/skills/jscodeshift/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add pproenca/dot-skills --skill jscodeshift -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/pproenca/dot-skills --path skills/.experimental/jscodeshift
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/jscodeshift/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add pproenca/dot-skills --skill jscodeshift -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/pproenca/dot-skills/tree/HEAD/skills/.experimental/jscodeshift/SKILL.md

## When to use it
- write a codemod to migrate a deprecated API
- debug a transform that fails on an unexpected node
- pick the right parser for TypeScript or Flow code
- strip unused imports after replacing code
- test a codemod on edge cases before running it repo-wide

## Example prompts
- help me write a jscodeshift codemod that replaces calls to the old API
- why does my transform fail on this file — walk through the jscodeshift rules
- check this codemod for edge cases and suggest tests

## Source text · SKILL.md · MIT

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: 71a3203d3adb3eb4.

BEGIN THIRD-PARTY FILE 71a3203d3adb3eb4
```text
---
name: jscodeshift
description: jscodeshift codemod development best practices from Facebook/Meta. This skill should be used when writing, reviewing, or debugging jscodeshift codemods. Triggers on tasks involving AST transformation, code migration, automated refactoring, or codemod development.
---

# Facebook/Meta jscodeshift Best Practices

Comprehensive best practices guide for jscodeshift codemod development, designed for AI agents and LLMs. Contains 40 rules across 8 categories, prioritized by impact from critical (parser configuration, AST traversal) to incremental (advanced patterns). Each rule includes detailed explanations, real-world examples, and specific impact metrics.

## When to Apply

Reference these guidelines when:
- Writing new jscodeshift codemods for code migrations
- Debugging transform failures or unexpected behavior
- Optimizing codemod performance on large codebases
- Reviewing codemod code for correctness
- Testing codemods for edge cases and regressions

## Rule Categories by Priority

| Priority | Category | Impact | Prefix |
|----------|----------|--------|--------|
| 1 | Parser Configuration | CRITICAL | `parser-` |
| 2 | AST Traversal Patterns | CRITICAL | `traverse-` |
| 3 | Node Filtering | HIGH | `filter-` |
| 4 | AST Transformation | HIGH | `transform-` |
| 5 | Code Generation | MEDIUM | `codegen-` |
| 6 | Testing Strategies | MEDIUM | `test-` |
| 7 | Runner Optimization | LOW-MEDIUM | `runner-` |
| 8 | Advanced Patterns | LOW | `advanced-` |

## Quick Reference

### 1. Parser Configuration (CRITICAL)

- [`parser-typescript-config`](references/parser-typescript-config.md) - Use correct parser for TypeScript files
- [`parser-flow-annotation`](references/parser-flow-annotation.md) - Use Flow parser for Flow-typed code
- [`parser-babel5-compat`](references/parser-babel5-compat.md) - Avoid default babel5compat for modern syntax
- [`parser-export-declaration`](references/parser-export-declaration.md) - Export parser from transform module
- [`parser-astexplorer-match`](references/parser-astexplorer-match.md) - Match AST Explorer parser to jscodeshift parser

### 2. AST Traversal Patterns (CRITICAL)

- [`traverse-find-specific-type`](references/traverse-find-specific-type.md) - Use specific node types in find() calls
- [`traverse-two-pass-pattern`](references/traverse-two-pass-pattern.md) - Use two-pass pattern for complex transforms
- [`traverse-early-return`](references/traverse-early-return.md) - Return early when no transformation needed
- [`traverse-find-filter-pattern`](references/traverse-find-filter-pattern.md) - Use find() with filter object over filter() chain
- [`traverse-closest-scope`](references/traverse-closest-scope.md) - Use closestScope() for scope-aware transforms
- [`traverse-avoid-repeated-find`](references/traverse-avoid-repeated-find.md) - Avoid repeated find() calls for same node type

### 3. Node Filtering (HIGH)
```
END THIRD-PARTY FILE 71a3203d3adb3eb4

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