Execute automatically formats and validates code files using Prettier and other formatting tools.
Use when users mention "format my code", "fix formatting", "apply code style",
"check formatting", "make code consistent", or "clean up code formatting".
Handles JavaScript, TypeScript, JSON, CSS, Markdown, and many other file types. Trigger with relevant phrases based on skill purpose.
Formats and validates code files using Prettier and related formatting tools. Supports JavaScript, TypeScript, JSON, CSS, Markdown, and many other file types.
Prerequisites
Node.js (v16+) and npm/npx installed
Prettier available globally (npm install -g prettier) or locally in the project
Write permissions for target files and configuration directories
Supported file types present in the project (.js, .jsx, .ts, .tsx, .json, .css, .md)
Instructions
Check whether Prettier is available by running . If missing, install it locally with or globally with .
npx prettier --version
npm install --save-dev prettier
npm install -g prettier
Detect existing configuration by searching for .prettierrc, .prettierrc.json, prettier.config.js, or a "prettier" key in package.json. If no configuration exists, create a .prettierrc with sensible defaults (see ${CLAUDE_SKILL_DIR}/references/implementation.md).
Run npx prettier --check "**/*.{js,jsx,ts,tsx,json,css,md}" --ignore-path .prettierignore to identify files that need formatting. Report the count and list of non-conforming files.
Apply formatting to identified files using npx prettier --write on the target paths. For single files, specify the exact path; for directories, use glob patterns.
Create or update .prettierignore to exclude generated outputs (dist/, build/, *.min.js, *.min.css), dependencies (node_modules/, vendor/), and lock files.
Optionally set up pre-commit enforcement by installing husky and lint-staged, then configuring lint-staged in package.json to run prettier --write on staged files matching supported extensions.
Run a final npx prettier --check to confirm all target files now conform to the configured style rules.
Output
A formatting execution report containing:
Count of files checked and files reformatted
List of files that were modified with before/after formatting status
Configuration file(s) created or updated (.prettierrc, .prettierignore)
Any git hook integration changes applied
Confirmation of final formatting compliance
Error Handling
Error
Cause
Solution
prettier: command not found
Prettier not installed globally or locally
Run npm install -g prettier or npx prettier --version to use npx
Syntax errors in source files
Malformed code that Prettier cannot parse
Fix syntax errors first using npx eslint --fix-dry-run <file> then retry formatting
Configuration conflicts
Multiple .prettierrc files or conflicting editorconfig
Locate all config files with find . -name ".prettier*" and consolidate to a single config
Permission denied on write
File or directory lacks write permission
Run chmod u+w <file> to grant write access
Parser not found for file type
Unsupported file extension or missing Prettier plugin
Install the appropriate Prettier plugin (e.g., prettier-plugin-svelte) or exclude the file type
Examples
Format a single file:
Trigger: "Format src/app.js"
Process: Run npx prettier --write src/app.js. Report the file as reformatted or already conformant.
Project-wide formatting setup:
Trigger: "Set up code formatting for this project."
Process: Create .prettierrc with project defaults, create .prettierignore excluding build outputs, run npx prettier --write "src/**/*.{js,ts,json,css}", install husky and lint-staged for pre-commit hooks, verify compliance.
Check formatting without modifying files:
Trigger: "Check formatting across the project."
Process: Run npx prettier --check "**/*.{js,jsx,ts,tsx,json,css,md}". Report non-conforming files with their paths. Suggest npx prettier --write to fix.
Resources
${CLAUDE_SKILL_DIR}/references/implementation.md -- detailed implementation guide with configuration examples
${CLAUDE_SKILL_DIR}/references/errors.md -- common error scenarios and solutions
