XO is an opinionated and minimal code linter and formatter for JavaScript and TypeScript. It helps developers maintain consistent code style and catch potential errors early in the development process. By enforcing a set of predefined rules, XO streamlines the coding workflow and reduces the time spent on manual code reviews and formatting.

Install XO

To begin using XO, you need to install it as a development dependency in your project. This is typically done using npm or yarn.

# Initialize XO in a JavaScript project, installing it as a development dependency
npm install --save-dev xo

Basic Usage

Once installed, you can run XO from your command line to lint files in your project. The tool automatically detects your project type and applies relevant rules.

# Lint files in the current directory
xo

# Lint files in a specific directory
xo ./src

Fixing Code Issues

XO can automatically fix many common code style issues. This feature is invaluable for quickly resolving formatting inconsistencies and minor errors.

# Fix issues automatically
xo --fix

# Fix issues and format files (e.g., enforcing spaces)
xo --fix --space

Configuration and Customization

While XO is opinionated, it offers flexibility through configuration files and command-line options to tailor its behavior to your project's specific needs.

# Lint files based on specific environment settings (like Node.js or browser)
xo --env=node

# Use a specific linter configuration file
xo --config=path/to/.xoconfig

# Lint files that match a specific pattern
xo "src/**/*.js"

# Customize rules directly in command line
xo --rule="semi: ['error', 'always']"

# Ignore a specific file or pattern
xo --ignore="ignored-file.js"

# Check specific file extensions
xo --extension=jsx

Help and Version Information

Accessing help and version information is straightforward with XO's command-line interface.

# Display the help and available options
xo --help

# Display the version number of XO
xo --version

External Resources

• XO GitHub Repository
• ESLint Configuration Guide (XO uses ESLint internally)
• MDN JavaScript Guide