How to display help when someone types an invalid option?

[toymachiner62]

If someone types in an option that doesn't exist, i want to display the --help text similarly to using program.help().

Where can i listen for errors such as this:

$ ./createUser -V
 error: unknown option `-V'

So that I can call program.help()?

[willxy]

This came up previously also in #482.

[Tarabass]

Does this help?

// Assert that a VALID command is provided 
if (!process.argv.slice(2).length || !/[arudl]/.test(process.argv.slice(2))) {
    program.outputHelp()
    process.exit()
}

[shadowspawn]

An answer was provided, and no further activity in a month. Closing this as resolved.

Feel free to open a new issue if it comes up again, with new information and renewed interest.

[trusktr]

In case someone stumbles here, this is how to show help when an invalid option was passed:

const cli = new commander.Command()

cli
	.description('...')
	.option(...)
	// ...
	.exitOverride(err => {
		// If an unknown option was passed, show help.
		if (err.code === 'commander.unknownOption') cli.help();
	});

cli.parse()

[shadowspawn]

Related: .showHelpAfterError() added in prerelease v8.0.0-2 by PR #1534