CLI Tool Project – `commander` in TypeScript

Install commander

npm i commander
npm i -D @types/commander

Basic CLI

#!/usr/bin/env node
import { Command } from 'commander';

const program = new Command();

program
  .name('calc')
  .description('Simple arithmetic calculator')
  .option('-v, --verbose', 'Enable verbose output')
  .argument('<a>', 'first operand', parseFloat)
  .argument('<b>', 'second operand', parseFloat)
  .argument('<op>', 'operation: add|sub|mul|div')
  .action((a: number, b: number, op: string, opts) => {
    let result: number;
    switch (op) {
      case 'add': result = a + b; break;
      case 'sub': result = a - b; break;
      case 'mul': result = a * b; break;
      case 'div':
        if (b === 0) { console.error('Division by zero'); process.exit(1); }
        result = a / b; break;
      default:
        console.error('Unknown operation'); process.exit(1);
    }
    if (opts.verbose) console.info(`Calculating ${a} ${op} ${b}`);
    console.log(result);
  });

program.parse();

Make the file executable (chmod +x cli.ts) and add a bin entry in package.json:

"bin": { "calc": "dist/cli.js" }

Build with tsc and publish.