Discussion: Web Components might be the right tool and save you time

[MrCrayon]

Hi!
First thing thanks for all great Tailwindlabs tools and I apologize if this is not the right channel, feel free to move this discussion or close it.

I am more of a backend guy but in my, admittedly low, knowledge of Web Components I think they might be the right tool to use for headlessui.

Quoting Adam

Right now just React and Vue, but we would like to explore other frameworks eventually. Just a lot of work to build a library like this for even one framework, have to start somewhere!

I totally understand that you already use Vue and React for your projects and do not want to invest too much time in other technologies but I really think building Web Components with Stenciljs is going to be pretty straight forward for you since it uses TypeScript and JSX and it will save you time since you only need to write once.
I have not worked previously with Stenciljs, TypeScript or React but I was able to port the switch component in half a day.

What would be the benefits of using Web Components instead of framework specific ones?

• One codebase that works with any framework, a thin wrapper might be needed.
• Can use components without any framework, drop them in your html and apply what's needed with alpine.js or vanilla javascript.
• IMHO code looks easier to read

I am no expert in front end development so in the next days I'm going to publish the code for everyone to check and find possible shortcomes.
Hopefully people more knowledgeable than me can contribute in the discussion.

Use with Alpine.js
Alpine.js component needs to be initialized after webcomponent has been rendered the first time

Click to show code

<div class="mt-6" x-data-defer="{ isChecked: true }">
  <h-switch
    class="flex items-center space-x-4"
    :checked="isChecked"
    @switched="isChecked = !isChecked"
  >
    <label label>Enable notifications</label>
    <button
      button
      class="relative inline-flex flex-shrink-0 h-6 transition-colors duration-200 ease-in-out border-2 border-transparent rounded-full cursor-pointer w-11 focus:outline-none focus:ring"
      :class="[ isChecked ? 'bg-indigo-600' : 'bg-gray-200' ]"
    >
      <span
        class="inline-block w-5 h-5 transition duration-200 ease-in-out transform bg-white rounded-full"
        :class="[ isChecked ? 'translate-x-5' : 'translate-x-0' ]"
      ></span>
    </button>
  </h-switch>
</div>

<script>
  const components = document.querySelectorAll("[x-data-defer]");
  components.forEach(comp => {
    comp.addEventListener("componentRendered", function handleConnected() {
      comp.setAttribute("x-data", comp.getAttribute("x-data-defer"));
      Alpine.initializeComponent(comp);
      comp.removeEventListener("componentRendered", handleConnected);
    });
  });
</script>

Use with Vue.js (vue-cli)
Vue.js needs to be configured to recognize custom elements

Click to show code

//vue.config.js
const vueConfig = {};

vueConfig.chainWebpack = config => {
  config.module
    .rule("vue")
    .use("vue-loader")
    .loader("vue-loader")
    .tap(options => {
      options.compilerOptions = {
        ...(options.compilerOptions || {}),
        isCustomElement: tag => /^h-/.test(tag),
      };
      return options;
    });
};

module.exports = vueConfig;

// main.js
import { defineCustomElements } from "headlessui-webcomponents/dist/esm/loader";

// Bind the custom elements to the window object
defineCustomElements();

// CustomSwitch.vue
<template>
  <div>
    <h-switch
      class="flex items-center space-x-4"
      :checked="modelValue"
      @switched="this.$emit('update:modelValue', $event.detail)"
    >
      <label label>{{ label }}</label>
      <button
        button
        class="w-11 focus:outline-none focus:ring relative inline-flex flex-shrink-0 h-6 transition-colors duration-200 ease-in-out border-2 border-transparent rounded-full cursor-pointer"
        :class="[modelValue ? 'bg-indigo-600' : 'bg-gray-200']"
      >
        <span
          class="inline-block w-5 h-5 transition duration-200 ease-in-out transform bg-white rounded-full"
          :class="[modelValue ? 'translate-x-5' : 'translate-x-0']"
        ></span>
      </button>
    </h-switch>
  </div>
</template>

<script>
export default {
  name: "CustomSwitch",
  emits: ["update:modelValue"],
  props: {
    modelValue: { type: Boolean, default: false },
    label: { type: String, default: "" },
  },
};
</script>

Use with React
I did not try with React but there are extensive instructions in Stencilejs website and Stencilejs should also be able to output React components that wrap the webcomponent.
https://stenciljs.com/docs/react

Use with Angular
I did not try with Angular but there are extensive instructions in Stencilejs website and Stencilejs.
https://stenciljs.com/docs/angular

Use with Ember
I did not try with Ember but there are extensive instructions in Stencilejs website and Stencilejs.
https://stenciljs.com/docs/ember

Implementation with Stenciljs
This is the switch component ported as webcomponent

Click to show code

import {
  Component,
  Element,
  Event,
  EventEmitter,
  h,
  Prop,
  State,
} from "@stencil/core";
import { Keys } from "../../utils/keyboard";
import { useId } from "../../hooks/use-id";

@Component({
  tag: "h-switch",
  shadow: false,
})
export class HSwitch {
  @Element() host: Element;

  /**
   * The status of checkbox
   */
  @Prop() checked: boolean = false;

  /**
   * Event emitted on status change
   */
  @Event({ bubbles: false }) switched: EventEmitter<boolean>;

  /**
   * Event emitted after component is rendered
   */
  @Event() componentRendered: EventEmitter;

  @State() button: HTMLButtonElement;
  @State() label: HTMLLabelElement;
  @State() id: number;

  // This is called only first time
  componentWillLoad() {
    this.id = useId();
    this.label = this.host.querySelector("[label]");
    this.button = this.host.querySelector("[button]");

    if (this.label) {
      this.label.id = "headlessui-switch-label-" + this.id;
      this.label.addEventListener("click", () => this.handleLabelClick());
    }

    this.button.id = "headlessui-switch-" + this.id;

    if (this.button.tagName === "BUTTON") {
      this.button.tabIndex = 0;
      this.label && this.button.setAttribute("aria-labelledby", this.label.id);
      this.button.setAttribute("role", "switch");
      this.button.addEventListener("click", e => this.handleClick(e));
      this.button.addEventListener("keyUp", e => this.handleKeyUp(e));
      this.button.addEventListener("keyPress", e => this.handleKeyPress(e));
    }
  }

  render() {
    this.button.setAttribute("aria-checked", this.checked.toString());

    return <slot></slot>;
  }

  componentDidRender() {
    this.componentRendered.emit();
  }

  private handleLabelClick() {
    this.button?.click();
    this.button?.focus({ preventScroll: true });
  }

  private handleClick(event) {
    event.preventDefault();
    this.toggle();
  }

  private handleKeyUp(event) {
    if (event.key !== Keys.Tab) event.preventDefault();
    if (event.key === Keys.Space) this.toggle();
  }

  private handleKeyPress(event) {
    event.preventDefault();
  }

  private toggle() {
    this.switched.emit(!this.checked);
  }
}

[xt0rted]

I've been working on a web components version for a couple of my projects, but recent events caused me to have to put it on hold. It's not public right now since it's mostly a proof of concept, but the current working version is on that page.

When github/catalyst was open sourced I started to replace some of my custom code with it and plan on looking into github/template-parts and github/jtml where appropriate. My hope is those will be application level dependencies and not needed for the component library.

I'm hoping to pick this back up next week and get the transition to catalyst finished up so I can make the repo public to get some feedback. I'll be sure to update this issue when I do.

[MrCrayon]

Edited my first comment with updated webcomponent code and code examples for Alpine and Vue.
Linked Stencilejs docs for React, Angula and Ember integrations.

@xt0rted any reason you are not considering stencilejs? I find the documentation quite good.
@kesne if you could provide your feedback on why you think this is a bad idea could be really helpful!

I found this nice comparison with frameworks to build webcomponents:
https://webcomponents.dev/blog/all-the-ways-to-make-a-web-component/

[RobinMalfait]

Hey! Thank you for your suggestion!
Much appreciated! 🙏

At this moment we don't really want to invest the time to switch to Web Components. In short, they didn't take off yet and they have a bunch of issues that I am not comfortable with. For example Accessibility related issues, children/slots are always rendered and they also require an additional runtime library to write them.

The examples you show also include decorators that are not supported yet, so we also would have to provide polyfills for those.

Once you want to port them to React, Vue, Angular, ... you still need some glue code. The goal of web components was to provide functionality that works everywhere. But in practice it still needs that glue code.

---

Maybe we will revisit this in the future, but not now.

[MrCrayon]

Thanks for your reply!
Naturally I respect your decision, I will keep exploring Web Components in my spare time hoping this might be useful in the future.
I published my code here https://github.com/MrCrayon/headlessui-webcomponents so hopefully someone else can join in the effort and we can discover if it's really doable.

I think it would be nice if we could keep the conversation here for who is interested to use headlessui in frameworks not yet supported but if you think receiving notifications from this issue is going to distract you right now just say the word I already opened the Discussions section in my repo.

About your specific issues for Web Components:

Accessibility
Did you have anything specific in mind? I did not find anything that is not related to shadow DOM (that we don't need) or that is not common with React or Vue components too.

Children/slots are always rendered
Yes but I only used the default slot, basically what the user writes is what is rendered plus the functionalities that the web component adds.
Switch component was the easier one so I'll try to understand if this can be done also with the other components.

Children/slots require an additional runtime library to write them
Not sure what you mean with that, if you write components with React or Stenciljs you are switching library it's not additional.

Decorators
I am too much of a newbe about mantaining packages to understand this.
When you run stenciljs compiler the end result is going to be some vanilla javascript files.
Most of the people will just need instructions on how to use them in their application and are not going to care if the web component was built with Typescript and decorators that btw are optional.

Glue code
To be honest, Alpinejs only needs to be initialized at the right time and for Vue, once is setup, you just need to create a component with your custom markup and style and that what's expected even using headlessui-vue package.
React is another story because of the way it manages attributes and events but that's hardly a Web Component fault and stencilejs is able to automatically do the wrapping and output React components.

Thanks and have a nice day!

[kerryj89]

I was excited when I read about Headless UI and how they remove the style opinionations. I assumed they did one further and made it framework-agnostic but was sadly mistakened. I agree that a forward-thinking approach would be to leverage something like StencilJS to transpile your components to support all popular SPA frameworks including the web-standard Web Components. New design systems are moving to using LitElement, FastElement, StencilJS, etc. to allow components to be used between different frameworks, and popular frameworks continue or already support Web Components out of the box. React is sadly behind in support but slowly they are moving to embracing it https://custom-elements-everywhere.com/