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TypeScript usage examples

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

The following .options() definition:

#!/usr/bin/env node
import * as yargs from 'yargs';

const argv = yargs.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'.