FirstParameter

Since 1.0.0

Get the first parameter type of a function.

Signature

typescript

type FirstParameter<T> = T extends (first: infer F, ...rest: any[]) => any ? F : never

Parameter	Description
`T`	The function type

Extracts the type of the first parameter from a function type.

typescript

import type { FirstParameter } from 'uni-types'

type Param = FirstParameter<(first: string, second: number) => void>
// string

typescript

type SingleParam = FirstParameter<(value: number) => void>
// number

typescript

type NoParam = FirstParameter<() => void> // never

typescript

type ObjParam = FirstParameter<(options: { a: string; b: number }) => void>
// { a: string; b: number }