Bootstrap - Collapse

bootstrap

What is the purpose of the collapse plugin?

It implements easy toggle behavior. Click the buttons below to show and hide another element via class changes:

  • .collapse: hides content
  • .collapsing: is applied during transitions
  • .collapse.in: shows content

You can use a link with the href attribute, or a button with the data-target attribute. In both cases, the data-toggle="collapse" is required.

<a class="btn btn-primary" 
    role="button" 
    data-toggle="collapse" 
    href="#collapseExample" 
    aria-expanded="false" 
    aria-controls="collapseExample">
  Link with href
</a>

<button class="btn btn-primary" 
    type="button" 
    data-toggle="collapse" 
    data-target="#collapseExample" 
    aria-expanded="false" 
    aria-controls="collapseExample">
  Button with data-target
</button>

<div class="collapse" id="collapseExample">
  <div class="well">
    ...
  </div>
</div>

In the above code, the link and the button either show or hide the content of the div.

What are the requirements for using the collapse plugin?

Collapse requires the transitions plugin to be included in your version of Bootstrap.

How can we use the collapse plugin to implement an accordion?

<div class="panel-group" id="accordion" role="tablist" aria-multiselectable="true">
  <div class="panel panel-default">
    <div class="panel-heading" role="tab" id="headingOne">
      <h4 class="panel-title">
        <a role="button" data-toggle="collapse" data-parent="#accordion" href="#collapseOne" aria-expanded="true" aria-controls="collapseOne">
          Collapsible Group Item #1
        </a>
      </h4>
    </div>
    <div id="collapseOne" class="panel-collapse collapse in" role="tabpanel" aria-labelledby="headingOne">
      <div class="panel-body">
        Some text ...
      </div>
    </div>
  </div>
  <div class="panel panel-default">
    <div class="panel-heading" role="tab" id="headingTwo">
      <h4 class="panel-title">
        <a class="collapsed" role="button" data-toggle="collapse" data-parent="#accordion" href="#collapseTwo" aria-expanded="false" aria-controls="collapseTwo">
          Collapsible Group Item #2
        </a>
      </h4>
    </div>
    <div id="collapseTwo" class="panel-collapse collapse" role="tabpanel" aria-labelledby="headingTwo">
      <div class="panel-body">
        Some text ...
      </div>
    </div>
  </div>
  <div class="panel panel-default">
    <div class="panel-heading" role="tab" id="headingThree">
      <h4 class="panel-title">
        <a class="collapsed" role="button" data-toggle="collapse" data-parent="#accordion" href="#collapseThree" aria-expanded="false" aria-controls="collapseThree">
          Collapsible Group Item #3
        </a>
      </h4>
    </div>
    <div id="collapseThree" class="panel-collapse collapse" role="tabpanel" aria-labelledby="headingThree">
      <div class="panel-body">
        Some text ...
      </div>
    </div>
  </div>
</div>

It's also possible to swap out .panel-bodys with .list-groups.

How can we make collapsible controls accessible?

Be sure to add aria-expanded to the control element. This attribute explicitly defines the current state of the collapsible element to screen readers and similar assistive technologies. If the collapsible element is closed by default, it should have a value of aria-expanded="false". If you've set the collapsible element to be open by default using the in class, set aria-expanded="true" on the control instead. The plugin will automatically toggle this attribute based on whether or not the collapsible element has been opened or closed.

Additionally, if your control element is targetting a single collapsible element – i.e. the data-target attribute is pointing to an id selector – you may add an additional aria-controls attribute to the control element, containing the id of 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.

How can we use collapse with the data attributes?

Just add data-toggle="collapse" and a data-target to the element to automatically assign control of a collapsible element. The data-target attribute accepts a CSS selector to apply the collapse to. Be sure to add the class collapse to the collapsible element. If you'd like it to default open, add the additional class in.

To add accordion-like group management to a collapsible control, add the data attribute data-parent="#selector".

How can we enable a collapsible control using JavaScript?

$('.collapse').collapse(options)

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

Name type default description
parent selector false If a selector is provided, then all collapsible elements under the specified parent will be closed when this collapsible item is shown. (similar to traditional accordion behavior - this is dependent on the panel class)
toggle boolean true Toggles the collapsible element on invocation

How can we toggle a collapsible control?

.collapse('toggle')

Toggles a collapsible element to shown or hidden. Returns to the caller before the collapsible element has actually been shown or hidden (i.e. before the shown.bs.collapse or hidden.bs.collapse event occurs).

How can we show a collapsible element?

.collapse('show')

Shows a collapsible element. Returns to the caller before the collapsible element has actually been shown (i.e. before the shown.bs.collapse event occurs).

How can we hide a collapsible element?

.collapse('hide')

Hides a collapsible element. Returns to the caller before the collapsible element has actually been hidden (i.e. before the hidden.bs.collapse event occurs).

What are the event types used by the collapsible plugin?

Event Type Description
show.bs.collapse This event fires immediately when the show instance method is called.
shown.bs.collapse This event is fired when a collapse element has been made visible to the user (will wait for CSS transitions to complete)
hide.bs.collapse This event is fired immediately when the hide method has been called.
hidden.bs.collapse This event is fired when a collapse element has been hidden from the user (will wait for CSS transitions to complete).
$('#myCollapsible').on('hidden.bs.collapse', function () {
  // do something…
})
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