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                <div class="disclosure" data-disclosure>
  <template data-disclosure-trigger-template>
    <button aria-expanded="false">Show/hide content</button>
  <div class="disclosure__content" data-disclosure-content>
    <p>This is the collapsable/expandable content</p>

<!-- Alternate, non PE-based approach: -->
<!-- <div class="disclosure" data-disclosure>
  <button aria-expanded="false" data-disclosure-trigger>Show/hide content</button>
  <div hidden class="disclosure__content" data-disclosure-content>
    <p>Lorem ipsum dolor sit amet consectetur adipisicing elit. Neque, aliquid esse nisi ut atque velit!</p>
    <p>Lorem ipsum, dolor sit amet consectetur adipisicing elit. Omnis quisquam expedita cum, saepe veritatis nulla delectus obcaecati voluptatem nihil dolore hic in, atque eligendi doloremque ab iste repellat, tempora eum.</p>
</div> -->


                /* Can handle toggled hiding in either CSS or JS (by toggling `hidden`).
The decision is sometimes arbitrary but I prefer CSS at the mo because it has more flexibility in hiding options. E.g. sometimes you’ll be animating so need to use CSS’s `visibility` because unlike hidden and display, it’s animatable.
If you are going the CSS route (which means creating a selector you wouldn’t need with the JS route), reuse the aria-expanded that’ll be on the button to DRY up the handling of different user experiences.
[aria-expanded="false"] + .disclosure__content {
  visibility: hidden;
/* end of note */

button {
  font-size: inherit;
  padding: 0.5em;

:root {
  font-size: 110%;
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, Helvetica, Arial,
    sans-serif, "Apple Color Emoji", "Segoe UI Emoji";



                const disclosure = document.querySelector("[data-disclosure]");
const btnTmpl = document.querySelector("[data-disclosure-trigger-template]");
const btnClone = btnTmpl.content.cloneNode(true);
const btn = btnClone.querySelector("button");
const disclosureContent = document.querySelector("[data-disclosure-content]");

btn.addEventListener("click", function () {
  let expanded = this.getAttribute("aria-expanded") === "true" || false;
  this.setAttribute("aria-expanded", !expanded);

disclosure.insertBefore(btnClone, disclosureContent);

// Alternate approach based on a "hidden" attribute on the content area// const disclosure = document.querySelector("[data-disclosure]");
// const triggerButton = document.querySelector("[data-disclosure-trigger]");
// const disclosureContent = document.querySelector("[data-disclosure-content]");
// disclosureContent.hidden = true;

// triggerButton.addEventListener("click", function () {
//   let expanded = this.getAttribute("aria-expanded") === "true" || false;
//   this.setAttribute("aria-expanded", !expanded);
//   disclosureContent.hidden = expanded ? true : false;
// });