@atlassian/aui/src/js/aui/expander.js

import $ from './jquery';

var $document = $(document);

//convenience function because this needs to be run for all the events.
var getExpanderProperties = function (event) {
    var properties = {};

    properties.$trigger = $(event.currentTarget);
    properties.$content = $document.find('#' + properties.$trigger.attr('aria-controls'));
    properties.triggerIsParent = properties.$content.parent().filter(properties.$trigger).length !== 0;
    properties.$shortContent = properties.triggerIsParent ? properties.$trigger.find('.aui-expander-short-content') : null;
    properties.height = properties.$content.css('min-height');
    properties.isCollapsible = properties.$trigger.data('collapsible') !== false;
    properties.replaceText = properties.$trigger.attr('data-replace-text'); //can't use .data here because it doesn't update after the first call
    properties.replaceSelector = properties.$trigger.data('replace-selector');

    return properties;
};

var replaceText = function (properties) {
    if (properties.replaceText) {
        var $replaceElement = properties.replaceSelector ?
            properties.$trigger.find(properties.replaceSelector) :
            properties.$trigger;

        properties.$trigger.attr('data-replace-text', $replaceElement.text());
        $replaceElement.text(properties.replaceText);
    }
};

//events that the expander listens to
var EXPANDER_EVENTS = {
    'aui-expander-invoke': function (event) {
        var $trigger = $(event.currentTarget);
        var $content = $document.find('#' + $trigger.attr('aria-controls'));
        var isCollapsible = $trigger.data('collapsible') !== false;

        //determine if content should be expanded or collapsed
        if ($content.attr('aria-expanded') === 'true' && isCollapsible) {
            $trigger.trigger('aui-expander-collapse');
        } else {
            $trigger.trigger('aui-expander-expand');
        }
    },

    'aui-expander-expand': function (event) {
        var properties = getExpanderProperties(event);

        // If the expander is already expanded, do nothing.
        if (properties.$content.attr('aria-expanded') === 'true') {
            return;
        }

        properties.$content.attr('aria-expanded', 'true');
        properties.$trigger.attr('aria-expanded', 'true');

        properties.$content.get(0).removeAttribute('hidden');

        //handle replace text
        replaceText(properties);

        //if the trigger is the parent also hide the short-content (default)
        if (properties.triggerIsParent) {
            properties.$shortContent.hide();
        }
        properties.$trigger.trigger('aui-expander-expanded');

    },

    'aui-expander-collapse': function (event) {
        var properties = getExpanderProperties(event);

        // If the expander is already collapsed, do nothing.
        if (properties.$content.attr('aria-expanded') !== 'true') {
            return;
        }

        //handle replace text
        replaceText(properties);

        //collapse the expander
        properties.$content.attr('aria-expanded', 'false');
        properties.$trigger.attr('aria-expanded', 'false');

        //if the trigger is the parent also hide the short-content (default)
        if (properties.triggerIsParent) {
            properties.$shortContent.show();
        }

        //handle the height option
        if (properties.$content.outerHeight() === 0) {
            properties.$content.get(0).setAttribute('hidden', '');
        }

        properties.$trigger.trigger('aui-expander-collapsed');
    },

    'click.aui-expander': function (event) {
        var $target = $(event.currentTarget);
        $target.trigger('aui-expander-invoke', event.currentTarget);
    }
};

//delegate events to the triggers on the page
$document.on(EXPANDER_EVENTS, '.aui-expander-trigger');