typescript.md

TypeScript usage examples

The TypeScript definitions take into account yargs' type key and the presence of demandOption/default.

The following .options() definition:

#!/usr/bin/env node
import yargs = require('yargs/yargs');

const argv = yargs(process.argv.slice(2)).options({
  a: { type: 'boolean', default: false },
  b: { type: 'string', demandOption: true },
  c: { type: 'number', alias: 'chill' },
  d: { type: 'array' },
  e: { type: 'count' },
  f: { choices: ['1', '2', '3'] }
}).argv;

Will result in an argv that's typed like so:

{
  [x: string]: unknown;
  a: boolean;
  b: string;
  c: number | undefined;
  d: (string | number)[] | undefined;
  e: number;
  f: string | undefined;
  _: string[];
  $0: string;
}

You will likely want to define an interface for your application, describing the form that the parsed argv will take:

interface Arguments {
  [x: string]: unknown;
  a: boolean;
  b: string;
  c: number | undefined;
  d: (string | number)[] | undefined;
  e: number;
  f: string | undefined;
}

To improve the choices option typing you can also specify its types:

type Difficulty = 'normal' | 'nightmare' | 'hell';
const difficulties: ReadonlyArray<Difficulty> = ['normal', 'nightmare', 'hell'];

const argv = yargs.option('difficulty', {
  choices: difficulties,
  demandOption: true
}).argv;

argv will get type 'normal' | 'nightmare' | 'hell'.