Commander.js

Trigger Scenarios

• Quickly create CLI scaffolding
• Define options and arguments
• Create subcommands
• Customize help information
• TypeScript support

Quick Start

// 1. Install
npm install commander

// 2. Create CLI
const { Command } = require('commander');
const program = new Command();

program
  .name('my-cli')
  .description('My CLI Tool')
  .version('1.0.0');

program.parse();

Option Definition

Basic Option Types

// Boolean option (no argument)
program.option('-d, --debug', 'Enable debug mode');

// Value option (requires argument)
program.option('-p, --port <number>', 'Server port', '3000');

// Optional value option
program.option('--cheese [type]', 'Add cheese (optional type)');

// Negated boolean option
program.option('--no-sauce', 'No sauce');

// Required option
program.requiredOption('-c, --cheese <type>', 'Must choose a cheese type');

// Variadic option (array)
program.option('--items <items...>', 'Multiple items');

Accessing Option Values

const options = program.opts();
console.log(options.debug); // or program.opts().debug

// Camel-case naming conversion: --template-engine → opts().templateEngine

Custom Option Processing

program.option('--date <date>', 'Date', (value) => new Date(value));

Subcommands

Inline Subcommands

program.command('serve')
  .description('Start server')
  .option('-p, --port <port>')
  .action((options) => {
    console.log('Server running on port', options.port);
  });

program.command('build')
  .description('Build project')
  .option('--watch')
  .action((options) => {
    console.log('Building...');
  });

Standalone Executable Subcommands

// Main program
program.command('git hooks', { isDefault: true });

// Subcommand file: commands/git-hook.js
#!/usr/bin/env node
console.log('Running git hook');

Argument Definition

// Required argument
program.argument('<file>', 'Input file');

// Optional argument
program.argument('[file]', 'Input file (optional)');

// Variadic argument
program.argument('<files...>', 'Multiple files');

// Access in action handler
program.command('split')
  .argument('<string>', 'String to split')
  .option('--separator <char>', 'Separator', ',')
  .action((str, options) => {
    console.log(str.split(options.separator));
  });

Help System

Automatic Help

node app.js --help
node app.js help command

Custom Help

program.on('option:help', () => {
  console.log('Custom help information');
  program.help();
});

program.addHelpCommand(false); // Disable help subcommand

Global Object Shortcut

For simple scripts, you can use the global object:

const { program } = require('commander');

program
  .name('my-tool')
  .option('-v, --verbose')
  .action(() => {
    console.log(program.opts().verbose ? 'Verbose mode' : 'Normal mode');
  });

program.parse();

TypeScript Support

import { Command } from 'commander';

const program = new Command();

program
  .name('ts-cli')
  .option('-n, --name <name>', 'Name')
  .action((options) => {
    console.log('Hello', options.name);
  });

program.parse();

Common Configuration

// Configure parsing behavior
program.configureOutput({
  writeErr: (str) => process.stderr.write(str),
  outputWidth: 80,
});

// Enable conflict checks
program.allowUnknownOption();
program.passThroughOptions();

// Lifecycle hooks
program
  .hook('preAction', (thisCommand) => {
    console.log('Pre-action hook');
  })
  .hook('postAction', (thisCommand) => {
    console.log('Post-action hook');
  });

Best Practices

1. Use a local Command object (not global) for easier unit testing
2. Always call program.parse() to start parsing
3. Prefer .option() over directly processing process.argv
4. Use camelCase option names for automatic conversion: --template-engine → opts().templateEngine
5. Use .description() to provide clear help information