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 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.

<div>
  <a class="nj-btn" data-toggle="collapse" href="#collapseExample" role="button" aria-expanded="false" aria-controls="collapseExample">
    Link with href
  </a>
  <button class="nj-btn" type="button" data-toggle="collapse" data-target="#collapseExample" aria-expanded="false" aria-controls="collapseExample">
    Button with data-target
  </button>
</div>
<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>

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.

<p>
  <a class="nj-btn" data-toggle="collapse" href="#multiCollapseExample1" role="button" aria-expanded="false" aria-controls="multiCollapseExample1">Toggle first element</a>
  <button class="nj-btn" type="button" data-toggle="collapse" data-target="#multiCollapseExample2" aria-expanded="false" aria-controls="multiCollapseExample2">Toggle second element</button>
  <button class="nj-btn" 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>

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="".

Methods

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.

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...
})