Solving Problems in Vue with Web Components

This is a bonus post in a series I'm working covering web components.

  1. Part 1: The Standards
  2. Part 2: The Polyfills
  3. Part 3: Vanilla Components

Part 4, on the Polymer library, is on the way. While we're waiting, check out this neat problem a student approached me with that we can solve with web standards:

They were using a library to render a WebGL globe inside a Vue component. They wanted to generate a set of markers and then track which markers were opened and which were closed. The WebGL library provided some APIs for attaching a string of innerHTML to each marker's popup, but didn't expose any APIs to track open, close, or click events.

I had a bit of a devilish thought 😈. If we can't add behaviour to the library popups, but we can add HTML, what if we added HTML that encapsulates its own behaviour?

🎩 Web Components to the Rescue!! 👨‍💻

Defining <popup-tooltip>

What we needed was an HTML element that fires an event every time it's containing popup opens or closes. The WebGL lib used style="visibility: visible" to open and close popups, so we'll create an element that uses MutationObserver to observe it's own parents.

class PopupTooltip extends HTMLElement {
  constructor() {
    this.observerCallback = this.observerCallback.bind(this);
    this.attachShadow({mode: 'open'});
    this.observer = new MutationObserver(this.observerCallback);

  connectedCallback() {
    // HACK: WebGL library toggles style.visibility on it's own
    // generated DOM to hide and show tooltips.
    const libraryContainer = this.parentElement.parentElement.parentElement;
    const config = { attributes: true, subtree: false, children: false };
    this.observer.observe(libraryContainer, config);

  observerCallback([{target}]) {
    const visible = target.style.visibility === 'visible';
    const type = 'popup-' + visible ? 'opened' : 'closed';
    const bubbles = true;
    const composed = true;
    const detail = this;
    this.dispatchEvent(new CustomEvent(type, { bubbles, composed, detail }));

customElements.define('popup-tooltip', PopupTooltip);

Connecting to the Vue Wrapper

So now we have a <popup-tooltip> element which will fire a popup-opened or popup-closed event any time it's container's visibility is toggled by the WebGL library. We set up listener's in the private DOM of the wrapping Vue Component:

<!-- WebGL lib instanciates on '#earth' -->
<div id="earth" @popup-opened="onPopupOpened" @popup-closed="onPopupClosed"></div>

Creating Each Popup

Then when we instantiated the WebGL lib and passed our data, we set up the markers to display a <popup-tooltip> element in it's tooltip content.

geoMarkers.forEach(marker => {
  const location = marker.latLng;
  const glMarker = new WebGLLib.popup({/*...*/});
  // NB: popupHTML is **just HTML**, there's no framework or library here.
  const popupHTML = `<popup-tooltip data-location="${location}">${marker.title}</popup-tooltip>`;
  // `bindPopup` is a method on our WebGL library's marker API.
  glMarker.bindPopup(popupHTML, config);


The last thing we had to do was track which popups were opened and which closed.

onPopupOpened({target: {dataset: {location}}}) {
  const [lat, lng] = location.split(',');
  console.log(`opened: lat: ${lat} lng: ${lng}`);

You don't need to give up your frameworks to use web components. You can use them anywhere you can use HTML and JavaScript. That's precisely what made web-components a win here: our GL library didn't take Vue components as input, it took a string of HTML.

See you in a few days for part 4 on the Polymer library.

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