tj/commander.js

Commander.js is a building block for making command-line programs in Node.js, the JavaScript runtime that runs outside the browser. A command-line program is the kind you run by typing its name in a terminal followed by some flags and arguments, like the example in the README that splits a string by a chosen separator. The hard, repetitive parts of writing such a program are parsing what the user typed, complaining when they misspell a flag, generating a help screen, and routing different verbs to different bits of your code. Commander handles all of that so you can focus on what your tool actually does. In practice you create a program object and then describe your interface by chaining method calls on it: .option to declare a flag.argument to declare a positional value.command to declare a subcommand, and .action to attach the function that should run for each subcommand. When you call .parse, Commander reads the arguments the user passed, fills in their values, and runs the right action. The README shows it being strict about unknown options, even suggesting the closest valid option when you mistype. It also generates a help command automatically, with the flag descriptions you supplied. Beyond the basics, the README mentions required and variadic options, life-cycle hooks, custom argument processing, stand-alone executable subcommands, error display overrides, and TypeScript support. You would reach for it whenever you are writing a Node.js command-line tool, from a tiny one-file utility to a multi-subcommand application like git. It is installed from npm under the name commander. The full README is longer than what was provided.