code: function ($container) {
        GOVUK.details.addEvent(document, 'DOMContentLoaded', GOVUK.details.addDetailsPolyfill)
        GOVUK.details.addEvent(window, 'load', GOVUK.details.addDetailsPolyfill)
      }
docs: 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