functional programming typescript extensions

fp.ts

type AnyFn = (...args: any[]) => any;

namespace ElementExt {
    export function addEventListener<
        El extends Element | Document,
        const S extends string,
        const H extends AnyFn,
    >(name: S, cb: H): (el: El) => void;
    export function addEventListener<
        El extends Element | Document,
        const S extends string,
        const H extends AnyFn,
    >(el: El, name: S, cb: H): void;
    export function addEventListener(
        arg0: string | (Element | Document),
        arg1: string | AnyFn,
        arg2?: EventListenerOrEventListenerObject,
    ) {
        if (typeof arg0 === "string" && typeof arg1 === "function") {
            return (el: Element) => el.addEventListener(arg0, arg1);
        }
        if ((arg0 instanceof Element || arg0 === document) && typeof arg1 === "string" && typeof arg2 === "function") {
            return arg0.addEventListener(arg1, arg2);
        }
        throw new Error("invalid arguments");
    }
}