Collapse

Collapses allow users to toggle the visibility of a content

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 height from its current value to 0. Given how CSS handles animations, you cannot use padding on a .nj-collapse element. Instead, use the class as an independent wrapping element.

Example

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

  • .nj-collapse hides content
  • .nj-collapsing is applied during transitions
  • .nj-collapse.show 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.

Anim pariatur cliche reprehenderit, enim eiusmod high life accusamus terry richardson ad squid. Nihil anim keffiyeh helvetica, craft beer labore wes anderson cred nesciunt sapiente ea proident.
<nj-collapse>
  <p>
    <a class="nj-btn nj-btn--primary" data-toggle="collapse" href="#collapseExample" role="button" aria-expanded="false" aria-controls="collapseExample">
      Link with href
    </a>
    <button class="nj-btn nj-btn--primary" type="button" data-toggle="collapse" data-target="#collapseExample" aria-expanded="false" aria-controls="collapseExample">
      Button with data-target
    </button>
  </p>
  <div class="nj-collapse" id="collapseExample">
    <div class="nj-card nj-card__body">
      Anim pariatur cliche reprehenderit, enim eiusmod high life accusamus terry richardson ad squid. Nihil anim keffiyeh helvetica, craft beer labore wes anderson cred nesciunt sapiente ea proident.
    </div>
  </div>
</nj-collapse>
Use only the tag <nj-collapse></nj-collapse> if you choose the Web Component initialization method with Angular, React or VueJs frameworks.

Multiple targets

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

Anim pariatur cliche reprehenderit, enim eiusmod high life accusamus terry richardson ad squid. Nihil anim keffiyeh helvetica, craft beer labore wes anderson cred nesciunt sapiente ea proident.
Anim pariatur cliche reprehenderit, enim eiusmod high life accusamus terry richardson ad squid. Nihil anim keffiyeh helvetica, craft beer labore wes anderson cred nesciunt sapiente ea proident.
<nj-collapse>
  <p>
    <a class="nj-btn nj-btn--primary" data-toggle="collapse" href="#multiCollapseExample1" role="button" aria-expanded="false" aria-controls="multiCollapseExample1">Toggle first element</a>
    <button class="nj-btn nj-btn--primary" type="button" data-toggle="collapse" data-target="#multiCollapseExample2" aria-expanded="false" aria-controls="multiCollapseExample2">Toggle second element</button>
    <button class="nj-btn nj-btn--primary" type="button" data-toggle="collapse" data-target=".multi-collapse" aria-expanded="false" aria-controls="multiCollapseExample1 multiCollapseExample2">Toggle both elements</button>
  </p>
  <div class="row">
    <div class="col">
      <div class="nj-collapse multi-collapse" id="multiCollapseExample1">
        <div class="nj-card nj-card__body">
          Anim pariatur cliche reprehenderit, enim eiusmod high life accusamus terry richardson ad squid. Nihil anim keffiyeh helvetica, craft beer labore wes anderson cred nesciunt sapiente ea proident.
        </div>
      </div>
    </div>
    <div class="col">
      <div class="nj-collapse multi-collapse" id="multiCollapseExample2">
        <div class="nj-card nj-card__body">
          Anim pariatur cliche reprehenderit, enim eiusmod high life accusamus terry richardson ad squid. Nihil anim keffiyeh helvetica, craft beer labore wes anderson cred nesciunt sapiente ea proident.
        </div>
      </div>
    </div>
  </div>
</nj-collapse>

Accessibility

Be sure to add aria-expanded to 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 show class, 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 collapsbile element). If the control element’s HTML element is not a button (e.g., an <a> or <div>), the attribute role="button" should be added to the element.

If your control element is targeting a single collapsible element – i.e. the data-target attribute is pointing to an id selector – you should add the 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.

Usage

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

  • .nj-collapse hides the content
  • .nj-collapse.show shows the content
  • .nj-collapsing is added when the transition starts, and removed when it finishes

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 Defaults Description
parent selector | DOM element false If parent is provided, then all collapsible elements under the specified parent will be closed when this collapsible item is shown. The attribute has to be set on the target collapsible area.
toggle boolean true Toggles the collapsible element on invocation

Methods

Method Description
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.nj.collapse or hidden.nj.collapse event occurs).
show Shows a collapsible element. Returns to the caller before the collapsible element has actually been shown (i.e. before the shown.nj.collapse event occurs).
hide Hides a collapsible element. Returns to the caller before the collapsible element has actually been hidden (i.e. before the hidden.nj.collapse event occurs).
dispose Destroys an element’s collapse.
var collapseNode = document.querySelector('#myCollapse')
var collapse = Collapse.getInstance(collapseNode)

collapse.toggle()
collapse.show()
collapse.hide()
collapse.dispose()

Events

Collapse class exposes a few events for hooking into collapse functionality.

Event Type Description
show.nj.collapse This event fires immediately when the show instance method is called.
shown.nj.collapse This event is fired when a collapse element has been made visible to the user (will wait for CSS transitions to complete).
hide.nj.collapse This event is fired immediately when the hide method has been called.
hidden.nj.collapse This event is fired when a collapse element has been hidden from the user (will wait for CSS transitions to complete).
document.querySelector('#myCollapse').addEventListener('show.nj.collapse', () => {
  // do something...
});
document.querySelector('#myCollapse').addEventListener('shown.nj.collapse', () => {
  // do something...
})
document.querySelector('#myCollapse').addEventListener('hide.nj.collapse', () => {
  // do something...
})
document.querySelector('#myCollapse').addEventListener('hidden.nj.collapse', () => {
  // do something...
})