3.2.0 • Public • Published

    Core Toggle

    @nrk/core-toggle makes a <button> toggle the visibility of next element sibling. Toggles can be nested and easily extended with custom animations or behavior through the toggle event.


    <button type="button">Popup VanillaJS</button>
    <core-toggle class="my-dropdown" popup hidden>
          <button type="button">Can also be nested</button>
          <core-toggle class="my-dropdown" popup hidden>
              <li><input type="text" autofocus aria-label="Skriv her"></li>
    <div id="jsx-toggle-popup"></div>
    <script type="text/jsx">
        <button type="button">Popup JSX</button>
        <CoreToggle className='my-dropdown' hidden popup onToggleSelect={console.warn}>
            <li><button type="button">Select</button></li>
            <li><a href='#'>Link</a></li>
              <button type="button">Can also be nested</button>
              <CoreToggle className='my-dropdown' hidden popup>
                  <li><a href='#'>Sub-link</a></li>
      </>, document.getElementById('jsx-toggle-popup'))


    Using NPM provides own element namespace and extensibility. Recommended:

    npm install @nrk/core-toggle  # Using NPM

    Using static registers the custom element with default name automatically:

    <script src="https://static.nrk.no/core-components/major/7/core-toggle/core-toggle.min.js"></script>  <!-- Using static -->

    Remember to polyfill custom elements if needed.


    HTML / JavaScript

    <button type="button">Toggle VanillaJS</button>       <!-- Must be <button> placed directly before <core-toggle> or use id + data-for attributes -->
      hidden                                <!-- Set hidden attribute to prevent FOUC -->
      popup="{String?}"                    <!-- Optional. If present, clicking outside open toggle will close it. Providing a string also enables select-behavior, by replacing value inside button with selected value, and suffixes provided string to aria-label on button -->
      Content                               <!-- Content to be toggled. Accepts text, elements and components -->
    import CoreToggle from '@nrk/core-toggle'                 // Using NPM
    window.customElements.define('core-toggle', CoreToggle)   // Using NPM. Replace 'core-toggle' with 'my-toggle' to namespace
    const myToggle = document.querySelector('core-toggle')
    // Getters
    myToggle.button         // Get toggle button element
    myToggle.popup          // Get popup value
    myToggle.hidden         // Get hidden value
    myToggle.value          // Get toggle button text
    // Setters
    myToggle.popup = {Boolean|String}   // If true, clicking outside open toggle will close it. Providing a string also enables select-behavior, by replacing value inside button with selected value, and suffixes provided string to aria-label on button
    myToggle.hidden = true              // Set hidden attribute
    myToggle.value = 'Velg'             // Sets innerHTML of the button and safely updates aria-label for screen readers. Defaults to button.innerHTML

    React / Preact

    import CoreToggle from '@nrk/core-toggle/jsx'
    <button type="button">Use with JSX</button>
      hidden                         // Set hidden attribute to prevent FOUC
      popup={Boolean|String}         // Optional. If true, clicking outside open toggle will close it. Providing a string also enables select-behavior, by replacing value inside button with selected value, and suffixes provided string to aria-label on button
      ref={(comp) => {}}             // Optional. Get reference to React component
      forwardRef={(el) => {}}        // Optional. Get reference to underlying DOM custom element
      onToggle={Function}            // Optional. Toggle event listener. See event 'toggle'
      onToggleSelect={Function}      // Optional. Toggle select event listener. See event 'toggle.select'
      Content                        // Content to be toggled. Accepts text, elements and components


    With for

    Putting the toggle button directly before the content is highly recommended, as this fulfills all accessibility requirements by default. There might be scenarios though, where styling makes this DOM structure impractical. In such cases, give the <button> a data-for attribute (for is deprecated), and the <core-toggle> an id with corresponding value. Make sure there is no text between the button and toggle content, as this will break the experience for screen reader users:

      <button data-for="my-toggle" type="button">Toggle</button>
    <core-toggle id="my-toggle" hidden>...</core-toggle>

    Popup and button HTML

    Using the popup attribute in conjunction with embedded HTML in your toggle button (an SVG icon for instance) will only preserve text when updating the value/label for the button. To preserve the embedded HTML, put the actual button text inside a <span>:

    <button type="button">
      <svg style="width:1.5em; height:1.5em" aria-hidden="true"><use xlink:href="#nrk-heart"></use></svg>
    <core-toggle popup="..." hidden>...</core-toggle>


    If you have form elements inside a <core-toggle>, you can optionally add a autofocus attribute to the most prominent form element. This helps the user navigate quickly when toggle is opened.


    When using core-toggle near the screen edges, the autoposition attribute positions the toggled content where there is visual room around the button, using position:fixed. This enables core-toggle to be used inside scrollable areas.

    <div style="overflow:auto; height:70px; width:200px; border:2px dashed #ccc;">
      <button type="button">Toggle is autopositioned</button>
      <core-toggle class="my-dropdown" autoposition hidden>
          <li><a>Another link</a></li>
          <li><a>Linking is life</a></li>
      <p>Scroll me to the edge!</p>



    Fired after open state changes:

    document.addEventListener('toggle', (event) => {
      event.target   // The toggle element


    Fired whenever an <a> or <button> element is selected inside a toggle with the popup option enabled. Useful for setting the value of the toggle button with the selected value.

    document.addEventListener('toggle.select', (event) => {
      event.target   // The toggle element
      event.detail   // The selected element
      event.target.value = event.detail  // Example: set value of toggle to selected element


    Note: <core-toggle> is display: inline by default. Change this by for instance setting core-toggle:not([hidden]) { display: block | flex | grid } or similar in your app. Not needed when position or float is used. All styling in documentation is example only. Both the <button> and <core-toggle> element receive attributes reflecting the current toggle state:

    .my-button {}                         /* Target button in any state */
    .my-button[aria-expanded="true"] {}   /* Target only open button */
    .my-button[aria-expanded="false"] {}  /* Target only closed button */
    .my-toggle-content {}                 /* Target content in any state */
    .my-toggle-content:not([hidden]) {}   /* Target only open content */
    .my-toggle-content[hidden] {}         /* Target only closed content */

    Example: Expand

    Content is only toggled when clicking the button. Great for accordions and expand/collapse panels.

    <button type="button">Toggle VanillaJS</button>  <!-- must be <button> -->
    <core-toggle hidden>Content</core-toggle>  <!-- hidden prevents flash of unstyled content -->
    <div id="jsx-toggle-default"></div>
    <script type="text/jsx">
        <button type="button">Toggle JSX</button>
        <CoreToggle hidden onToggle={console.log}>Content</CoreToggle>
      </>, document.getElementById('jsx-toggle-default'))

    Example: Select

    popup-attribute is required for Select behavior

    Listen to the toggle.select event and update the button's value from the selected item to create a component that behaves like a <select>:

    <button type="button">Episode 1</button>
    <core-toggle class="my-select my-dropdown" hidden popup="Choose episode">
        <li><button type="button">Episode 1</button></li>
        <li><button type="button">Episode 2</button></li>
        <li><button type="button">Episode 3</button></li>
      document.addEventListener('toggle.select', (event) => {
        if (!event.target.classList.contains('my-select')) return
        event.target.value = event.detail
        event.target.hidden = true
    <div id="jsx-toggle-select"></div>
    <script type="text/jsx">
      class MyToggleSelect extends React.Component {
        constructor (props) {
          this.state = { value: 'Select number' }
          this.onSelect = this.onSelect.bind(this)
        onSelect (event) {
          event.target.hidden = true
          this.setState({ value: event.detail.textContent })
        render () {
          return <>
            <button type="button">{this.state.value}</button>
            <CoreToggle className='my-dropdown' popup='Example picker' hidden onToggleSelect={this.onSelect}>
                <li><button type="button">One</button></li>
                <li><button type="button">Two</button></li>
                <li><button type="button">Three</button></li>
      ReactDOM.render(<MyToggleSelect/>, document.getElementById('jsx-toggle-select'))


    Why not use <details> instead?

    Despite having a native <details> element for expanding/collapsing content, there are several issues regarding browser support, styling, accessibility. Furthermore, polyfills often conflict with other standards such as <dialog>.

    Why is there no role="menu" in dropdowns?

    The menu role is mainly inteded for context menues and toolbars in application interfaces, and has quite complex keyboard navigation requirements. As most end users will not expect application behavior in websites and internal web based systems, (implemented) attributes like aria-controls and aria-labelledby is sufficient for a good user experience.

    Why does dropdowns not open on hover?

    Both touch devices and screen readers will have trouble properly interacting with hoverable interfaces (unless more complex fallback logic is implemented). To achieve a consistent and accessible interface, <core-toggle> is designed around click interactions.

    Why is there no group-option to achieve a single open toggle?

    Some expand/collapse interfaces like accordions behaves like a group - allowing only one expanded area at the time. This pattern however requires more logic and carefully designed animations to avoid confusion over expected scroll position.

    Example: The user first opens "Toggle-1", and then "Toggle-2" (which closes "Toggle-1"). Since "Toggle-1" is placed above, the position "Toggle-2" now changes - potentially outside the viewport on smaller devices. Note: If you do need to implement grouping, you can achieve this by reacting to the toggle event.




    npm i @nrk/core-toggle

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