sveltekit stuff

Types

The npm package exports these utility types:

Types

typescript 
export type FirstArgOf<T> = T extends (first: infer FirstArgument, ...args: any[]) => any
	? FirstArgument
	: never;

export type SecondArgOf<T> = T extends (
	first: any,
	second: infer SecondArgument,
	...args: any[]
) => any
	? SecondArgument
	: never;

/**
 * Thank you Matt Pocock
 * {@link https://twitter.com/mattpocockuk/status/1622730173446557697}
 */
export type Prettify<T> = {
	[K in keyof T]: T[K];
} & {};

export type Optional<T> = T | undefined;

The arg inferral types can be useful in svelte for example when storing transitions / actions and their params in variables like so:

Example

typescript 
import type { SecondArgOf } from '$lib/types';
import { fly } from 'svelte/transition';

export const ROUTE_TRANSITION = fly;
export const ROUTE_TRANSITION_PARAMS: SecondArgOf<typeof ROUTE_TRANSITION> = {
	// Infers FlyParams
	duration: 250,
	opacity: 0,
	x: 300
};

The Prettify-type is just cool.

NPM version