rambdax/_ts-toolbelt/src/Function/Length.ts

Extended version of Rambda - a lightweight, faster alternative to Ramda

import {Function} from './Function'
import {Parameters} from './Parameters'
import {Formats} from '../Iteration/_Internal'
import {Length as LLength} from '../List/Length'

/**
Extract arguments' length from a [[Function]]
@param F to extract from
@param fmt (?=`'n'`) output
@returns [[String]] or `number`
@example
```ts
import {F} from 'ts-toolbelt'

const fn = (a1: any, a2: any) => {}

type test0 = F.LengthOf<typeof fn>               // 2

type test1 = F.LengthOf<(a1?: any) => any>       // 0 | 1

type test2 = F.LengthOf<(...a: any[]) => any>    // number
```
*/
export type Length<Fn extends Function, fmt extends Formats = 'n'> =
    LLength<Parameters<Fn>, fmt>