*preact-options-helper.md

import { hook, OptionsTypes } from './preact-options-helper.ts';

hook(OptionsTypes.RENDER, (old, vnode) => {
    let component = vnode.__c;
    if (component) {
        // do stuff with the component instance
    } else {
        console.log(vnode.props);
    }
    old(vnode); // invoke the next options hook in the chain
});

preact-hooks-helper.ts

import { options } from "preact";

export interface VNode<P = any> extends preact.VNode<P> {
    /** The component instance for this VNode */
    __c: AugmentedComponent;
    /** The parent VNode */
    __?: VNode;
    /** The DOM node for this VNode */
    __e?: Element | Text;
    /** Props that had Signal values before diffing (used after diffing to subscribe) */
    __np?: Record<string, any> | null;
}

export const enum OptionsTypes {
    HOOK = "__h",
    DIFF = "__b",
    DIFFED = "diffed",
    RENDER = "__r",
    CATCH_ERROR = "__e",
    UNMOUNT = "unmount",
}

interface OptionsType {
    [OptionsTypes.HOOK](component: Component, index: number, type: number): void;
    [OptionsTypes.DIFF](vnode: VNode): void;
    [OptionsTypes.DIFFED](vnode: VNode): void;
    [OptionsTypes.RENDER](vnode: VNode): void;
    [OptionsTypes.CATCH_ERROR](error: any, vnode: VNode, oldVNode: VNode): void;
    [OptionsTypes.UNMOUNT](vnode: VNode): void;
}

/** Install a Preact options hook */
export function hook<T extends OptionsTypes>(hookName: T, hookFn: HookFn<T>) {
    // @ts-ignore-next-line private options hooks usage
    options[hookName] = hookFn.bind(null, options[hookName] || (() => {}));
}