2022-11-01
2641
#react
Alexander Solovyev
11344
Nov 1, 2022 â‹… 9 min read

Learn React Portals by example

Alexander Solovyev Frontend developer and mentor @mkdev.me

Recent posts:

How To Integrate WunderGraph With Your Frontend Application

How to integrate WunderGraph with your frontend application

Unify and simplify APIs using WunderGraph to integrate REST, GraphQL, and databases in a single endpoint.

Boemo Mmopelwa
May 17, 2024 â‹… 5 min read
Understanding The Latest Webkit Features In Safari 17.4

Understanding the latest Webkit features in Safari 17.4

The Safari 17.4 update brought in many modern features and bug fixes. Explore the major development-specific updates you should be aware of.

Rahul Chhodde
May 16, 2024 â‹… 10 min read
Using Webrtc To Implement Peer To Peer Video Streaming In A Node Js Project

Using WebRTC to implement P2P video streaming

Explore one of WebRTC’s major use cases in this step-by-step tutorial: live peer-to-peer audio and video streaming between systems.

Oduah Chigozie
May 16, 2024 â‹… 18 min read
Htmx Vs React

htmx vs. React: Choosing the right library for your project

Both htmx and React provide powerful tools for building web apps, but in different ways that are suited to different types of projects.

Temitope Oyedele
May 15, 2024 â‹… 9 min read
View all posts

8 Replies to "Learn React Portals by example"

  1. I observed a problem in this and I thought it’s important to notify, else a lot of other people might make the same mistake.

    In the `Portal` component, you are using `useEffect` with `el` and `mount` as dependencies and that actually causes unnecessary re-renders even if the prop(children in this case) of the Portal component hasn’t changed. Meaning if there is any change in the parent component which isn’t related to the Portal also, the Portal gets re-rendered.

    example:Try adding say a state variable `count` in the parent component and change the value when the modal is shown, although there is no change in portal, it would still re-render the portal which is bad.

    One Solution is to move the `mount` and `el` outside the Portal component. This still re-renders the Portal but it doesn’t mount the portal content again which would trigger useEffect otherwise as its not a new instance of either `el` or `mount`.

    Other solution would be to use the class component. But please be careful when you are demonstrating something with hooks. I think we underestimate the complexity of the hooks in most cases, and in the end we shoot in our own foot.

  2. @Brihaspati thanks for feedback. Yes, I confirm that my implementation of Portal is naive and could be improved for performance.

    Instead of just moving the el and mount outside of the component there is also an option to use some of the React hooks that keep variables between renders, for example, useRef:
    “`
    import { useEffect, useRef, memo } from “react”;
    import { createPortal } from “react-dom”;

    const Portal = ({ children }) => {
    /**
    * keeps ref between renders
    */
    const el = useRef(null);

    /**
    * create element if empty (for the first time render only)
    */
    if (!el.current) el.current = document.createElement(“div”);

    useEffect(() => {
    const mount = document.getElementById(“portal-root”);
    const { current } = el;

    mount.appendChild(current);
    return () => mount.removeChild(current);
    }, []); // no dependencies to avoid rerenders

    return createPortal(children, el.current);
    };

    export default memo(Portal);
    “`
    here is a live demo for it https://codesandbox.io/s/portal-with-hooks-70pyc

    You could also check other possible implementations of React Portal with hooks in this stackoverflow thread: https://stackoverflow.com/questions/53595935/how-can-i-make-react-portal-work-with-react-hook

  3. Hi! I was curious why we need the “el” to be appended? I tried with directly appending to the mount point in the DOM and it works as well. Does the “el” pattern help with something I am not seeing?

  4. Hi Muhammad, the el pattern is used for enabling the option of multiple portal items on the page: each portal appends its own element to the portal mount point. That might be helpful, for example, if there are multiple small popups on the page that should be kept open at the same time

  5. There’s an issue when the portal rerenders because the portal element is removed and rappended inside the useEffect hook, there’s no portal element to render to so the portal’s children content is absent. I fixed this by replacing the useEffect hook with useLayoutEffect to block react until the portal is rendered. Fortunately this is unnecessary if you instead store the portal element between rerenders like what is done above.

  6. I found a flaw following this implementation approach, which is that when the button is in the local scrolling area, clicking the button opens the tips. When scrolling, the tips will not follow. Using global scrolling does not have this problem because the tips do not scroll relative to the body

Leave a Reply