details.js

// ===========================
// UPDATE MAY 2020
// A bug with Voiceover is currently hiding details elements from the Rotor when using the native details element
// The Elements polyfill is being used to by-pass this bug and add in additional aria information missing in the current GOVUK Frontend version
// ===========================

// This is the Elements details polyfill updated to ensure focussable elements inside it are not exposed
// This is accomplished by adding display none to the internal content wrapper.

// <details> polyfill
// http://caniuse.com/#feat=details

// FF Support for HTML5's <details> and <summary>
// https://bugzilla.mozilla.org/show_bug.cgi?id=591737

// http://www.sitepoint.com/fixing-the-details-element/

; (function (global) {
  'use strict'

  var GOVUK = global.GOVUK || {}

  GOVUK.details = {
    NATIVE_DETAILS: typeof document.createElement('details').open === 'boolean',
    KEY_ENTER: 13,
    KEY_SPACE: 32,

    // Create a started flag so we can prevent the initialisation
    // function firing from both DOMContentLoaded and window.onload
    started: false,

    // Add event construct for modern browsers or IE
    // which fires the callback with a pre-converted target reference
    addEvent: function (node, type, callback) {
      if (node.addEventListener) {
        node.addEventListener(type, function (e) {
          callback(e, e.target)
        }, false)
      } else if (node.attachEvent) {
        node.attachEvent('on' + type, function (e) {
          callback(e, e.srcElement)
        })
      }
    },

    removeEvent: function (node, type) {
      if (node.removeEventListener) {
        node.removeEventListener(type, function (e) {
        }, false)
      } else if (node.detachEvent) {
        node.detachEvent('on' + type, function (e) {
        })
      }
    },

    // Cross-browser character code / key pressed
    charCode: function (e) {
      return (typeof e.which === 'number') ? e.which : e.keyCode
    },

    // Cross-browser preventing default action
    preventDefault: function (e) {
      if (e.preventDefault) {
        e.preventDefault()
      } else {
        e.returnValue = false
      }
    },

    // Handle cross-modal click events
    addClickEvent: function (node, callback) {
      GOVUK.details.addEvent(node, 'keypress', function (e, target) {
        // When the key gets pressed - check if it is enter or space
        if (GOVUK.details.charCode(e) === GOVUK.details.KEY_ENTER || GOVUK.details.charCode(e) === GOVUK.details.KEY_SPACE) {
          if (target.nodeName.toLowerCase() === 'summary') {
            // Prevent space from scrolling the page
            // and enter from submitting a form
            GOVUK.details.preventDefault(e)
            // Click to let the click event do all the necessary action
            if (target.click) {
              target.click()
            } else {
              // except Safari 5.1 and under don't support .click() here
              callback(e, target)
            }
          }
        }
      })

      // Prevent keyup to prevent clicking twice in Firefox when using space key
      GOVUK.details.addEvent(node, 'keyup', function (e, target) {
        if (GOVUK.details.charCode(e) === GOVUK.details.KEY_SPACE) {
          if (target.nodeName === 'SUMMARY') {
            GOVUK.details.preventDefault(e)
          }
        }
      })

      GOVUK.details.addEvent(node, 'click', function (e, target) {
        callback(e, target)
      })
    },

    // Get the nearest ancestor element of a node that matches a given tag name
    getAncestor: function (node, match) {
      do {
        if (!node || node.nodeName.toLowerCase() === match) {
          break
        }
        node = node.parentNode
      } while (node)

      return node
    },

    // Initialisation function
    addDetailsPolyfill: function (list, container) {
      container = container || document.body
      // If this has already happened, just return
      // else set the flag so it doesn't happen again
      if (GOVUK.details.started) {
        return
      }
      GOVUK.details.started = true
      // Get the collection of details elements, but if that's empty
      // then we don't need to bother with the rest of the scripting
      if ((list = container.getElementsByTagName('details')).length === 0) {
        return
      }
      // else iterate through them to apply their initial state
      var n = list.length
      var i = 0
      for (i; i < n; i++) {
        var details = list[i]

        // Save shortcuts to the inner summary and content elements
        details.__summary = details.getElementsByTagName('summary').item(0)
        details.__content = details.getElementsByTagName('div').item(0)

        if (!details.__summary || !details.__content) {
          return
        }
        // If the content doesn't have an ID, assign it one now
        // which we'll need for the summary's aria-controls assignment
        if (!details.__content.id) {
          details.__content.id = 'details-content-' + i
        }

        // Add ARIA role="group" to details
        details.setAttribute('role', 'group')

        // Add role=button to summary
        details.__summary.setAttribute('role', 'button')

        // Add aria-controls
        details.__summary.setAttribute('aria-controls', details.__content.id)

        // Set tabIndex so the summary is keyboard accessible for non-native elements
        // http://www.saliences.com/browserBugs/tabIndex.html
        if (!GOVUK.details.NATIVE_DETAILS) {
          details.__summary.tabIndex = 0
        }

        // Detect initial open state
        var openAttr = details.getAttribute('open') !== null
        if (openAttr === true) {
          details.__summary.setAttribute('aria-expanded', 'true')
          details.__content.setAttribute('aria-hidden', 'false')
        } else {
          details.__summary.setAttribute('aria-expanded', 'false')
          details.__content.setAttribute('aria-hidden', 'true')
          // UPDATE MAY 2020 removed NATIVE_DETAILS check for style update
          // if (!GOVUK.details.NATIVE_DETAILS) {
              details.__content.style.display = 'none'
          // }
        }

        // Create a circular reference from the summary back to its
        // parent details element, for convenience in the click handler
        details.__summary.__details = details


        // UPDATE MAY 2020
        // removed additional arrow as this is handled by the newer GOV Frontend CSS

        // If this is not a native implementation, create an arrow
        // inside the summary
        // if (!GOVUK.details.NATIVE_DETAILS) {
        //   var twisty = document.createElement('i')

        //   if (openAttr === true) {
        //     twisty.className = 'arrow arrow-open'
        //     twisty.appendChild(document.createTextNode('\u25bc'))
        //   } else {
        //     twisty.className = 'arrow arrow-closed'
        //     twisty.appendChild(document.createTextNode('\u25ba'))
        //   }

        //   details.__summary.__twisty = details.__summary.insertBefore(twisty, details.__summary.firstChild)
        //   details.__summary.__twisty.setAttribute('aria-hidden', 'true')
        // }
      }

      // Bind a click event to handle summary elements
      GOVUK.details.addClickEvent(container, function (e, summary) {
        if (!(summary = GOVUK.details.getAncestor(summary, 'summary'))) {
          return true
        }
        return GOVUK.details.statechange(summary)
      })
    },

    // Define a statechange function that updates aria-expanded and style.display
    // Also update the arrow position
    statechange: function (summary) {
      var expanded = summary.__details.__summary.getAttribute('aria-expanded') === 'true'
      var hidden = summary.__details.__content.getAttribute('aria-hidden') === 'true'

      summary.__details.__summary.setAttribute('aria-expanded', (expanded ? 'false' : 'true'))
      summary.__details.__content.setAttribute('aria-hidden', (hidden ? 'false' : 'true'))

      // UPDATE MAY 2020 - moved style update out of NATIVE_DETAILS check
      summary.__details.__content.style.display = (expanded ? 'none' : '')
      if (!GOVUK.details.NATIVE_DETAILS) {


        var hasOpenAttr = summary.__details.getAttribute('open') !== null
        if (!hasOpenAttr) {
          summary.__details.setAttribute('open', 'open')
        } else {
          summary.__details.removeAttribute('open')
        }
      }

      if (summary.__twisty) {
        summary.__twisty.firstChild.nodeValue = (expanded ? '\u25ba' : '\u25bc')
        summary.__twisty.setAttribute('class', (expanded ? 'arrow arrow-closed' : 'arrow arrow-open'))
      }

      return true
    },

    destroy: function (node) {
      GOVUK.details.removeEvent(node, 'click')
    },

    // Bind two load events for modern and older browsers
    // If the first one fires it will set a flag to block the second one
    // but if it's not supported then the second one will fire
    init: function ($container) {
      GOVUK.details.addEvent(document, 'DOMContentLoaded', GOVUK.details.addDetailsPolyfill)
      GOVUK.details.addEvent(window, 'load', GOVUK.details.addDetailsPolyfill)
    }
  }
  global.GOVUK = GOVUK
})(window)