collapse

How it works

The collapse JavaScript plugin is used to show and hide content. Buttons or anchors are used as triggers that are mapped to specific elements you toggle. Collapsing an element will animate the heightfrom its current value to 0. Given how CSS handles animations, you cannot use paddingon a .collapseelement. Instead, use the class as an independent wrapping element.

example

Click the buttons below to show and hide another element via class changes:

• .collapsehides content
• .collapsingis applied during transitions
• .collapse.showshow content

Generally, we recommend using a button with the data-bs-targetattribute. While not recommended from a semantic point of view, you can also use a link with the hrefattribute (and a role="button"). In both cases, the data-bs-toggle="collapse"is required.

<p>
  <a class="btn btn-primary" data-bs-toggle="collapse" href="#collapseExample" role="button" aria-expanded="false" aria-controls="collapseExample">
    Link with href
  </a>
  <button class="btn btn-primary" type="button" data-bs-toggle="collapse" data-bs-target="#collapseExample" aria-expanded="false" aria-controls="collapseExample">
    Button with data-bs-target
  </button>
</p>
<div class="collapse" id="collapseExample">
  <div class="card card-body">
    Some placeholder content for the collapse component. This panel is hidden by default but revealed when the user activates the relevant trigger.
  </div>
</div>

multiple targets

A <button>or <a>can show and hide multiple elements by referencing them with a selector in its hrefor data-bs-targetattribute. Multiple <button>or <a>can show and hide an element if they each reference it with their hrefor data-bs-targetattribute

<p>
  <a class="btn btn-primary" data-bs-toggle="collapse" href="#multiCollapseExample1" role="button" aria-expanded="false" aria-controls="multiCollapseExample1">Toggle first element</a>
  <button class="btn btn-primary" type="button" data-bs-toggle="collapse" data-bs-target="#multiCollapseExample2" aria-expanded="false" aria-controls="multiCollapseExample2">Toggle second element</button>
  <button class="btn btn-primary" type="button" data-bs-toggle="collapse" data-bs-target=".multi-collapse" aria-expanded="false" aria-controls="multiCollapseExample1 multiCollapseExample2">Toggle both elements</button>
</p>
<div class="row">
  <div class="col">
    <div class="collapse multi-collapse" id="multiCollapseExample1">
      <div class="card card-body">
        Some placeholder content for the first collapse component of this multi-collapse example. This panel is hidden by default but revealed when the user activates the relevant trigger.
      </div>
    </div>
  </div>
  <div class="col">
    <div class="collapse multi-collapse" id="multiCollapseExample2">
      <div class="card card-body">
        Some placeholder content for the second collapse component of this multi-collapse example. This panel is hidden by default but revealed when the user activates the relevant trigger.
      </div>
    </div>
  </div>
</div>

accessibility

Be sure to add aria-expandedto the control element. This attribute explicitly conveys the current state of the collapsible element tied to the control to screen readers and similar assistive technologies. If the collapsible element is closed by default, the attribute on the control element should have a value of aria-expanded="false". If you've set the collapsible element to be open by default using the showclass, set aria-expanded="true"on the control instead. The plugin will automatically toggle this attribute on the control based on whether or not the collapsible element has been opened or closed (via JavaScript, or because the user triggered another control element also tied to the same collapsible element). If the control element's HTML element is not a button (eg, an <a>or <div>), the attributerole="button"should be added to the element.

If your control element is targeting a single collapsible element – ​​ie the data-bs-targetattribute is pointing to an idselector – you should add the aria-controlsattribute to the control element, containing the idof the collapsible element. Modern screen readers and similar assistive technologies make use of this attribute to provide users with additional shortcuts to navigate directly to the collapsible element itself.

Note that Bootstrap's current implementation does not cover the various optional keyboard interactions described in the WAI-ARIA Authoring Practices 1.1 accordion pattern - you will need to include these yourself with custom JavaScript.

Sass

Variables

$transition-collapse:         height .35s ease;

classes

Collapse transition classes can be found in scss/_transitions.scssas these are shared across multiple components (collapse and accordion).

.collapse {
  &:not(.show) {
    display: none;
  }
}

.collapsing {
  height: 0;
  overflow: hidden;
  @include transition($transition-collapse);
}

Usage

The collapse plugin utilizes a few classes to handle the heavy lifting:

• .collapsehides the content
• .collapse.showshows the content
• .collapsingis added when the transition starts, and removed when it finishes

These classes can be found in _transitions.scss.

Via data attributes

Just add data-bs-toggle="collapse"and a data-bs-targetto the element to automatically assign control of one or more collapsible elements. The data-bs-targetattribute accepts a CSS selector to apply the collapse to. Be sure to add the class collapseto the collapsible element. If you'd like it to default open, add the additional class show.

To add accordion-like group management to a collapsible area, add the data attribute data-bs-parent="#selector". Refer to the demo to see this in action.

Via JavaScript

Enable manually with:

var collapseElementList = [].slice.call(document.querySelectorAll('.collapse'))
var collapseList = collapseElementList.map(function (collapseEl) {
  return new bootstrap.Collapse(collapseEl)
})

Options

Options can be passed via data attributes or JavaScript. For data attributes, append the option name to data-bs-, as in data-bs-parent="".

methods

Activates your content as a collapsible element. Accepts an optional options object.

You can create a collapse instance with the constructor, for example:

var myCollapse = document.getElementById('myCollapse')
var bsCollapse = new bootstrap.Collapse(myCollapse, {
  toggle: false
})

Events

Bootstrap's collapse class exposes a few events for hooking into collapse functionality.

var myCollapsible = document.getElementById('myCollapsible')
myCollapsible.addEventListener('hidden.bs.collapse', function () {
  // do something...
})