wikimedia/mediawiki-extensions-Wikibase

// Copied from mediawiki-core's mediawiki.action.edit.collapsibleFooter.js
( function () {
    'use strict';

    var collapsibleLists, handleOne;

    // Collapsible lists of categories and templates
    collapsibleLists = [
        {
            listSel: '.wikibase-entity-usage ul',
            togglerSel: '.wikibase-entityusage-explanation',
            storeKey: 'mwedit-state-wikibaseEntityUsage'
        }
    ];

    handleOne = function ( $list, $toggler, storeKey ) {
        var collapsedVal = '0',
            expandedVal = '1',
            // Default to collapsed if not set
            isCollapsed = mw.storage.get( storeKey ) !== expandedVal;

        // Style the toggler with an arrow icon and add a tabIndex and a role for accessibility
        $toggler.addClass( 'mw-editfooter-toggler' ).prop( 'tabIndex', 0 ).attr( 'role', 'button' );
        $list.addClass( 'mw-editfooter-list' );

        $list.makeCollapsible( {
            $customTogglers: $toggler,
            linksPassthru: true,
            plainMode: true,
            collapsed: isCollapsed
        } );

        if ( isCollapsed ) {
            $toggler.addClass( 'mw-editfooter-toggler-collapsed' );
        }

        $list.on( 'beforeExpand.mw-collapsible', function () {
            $toggler.removeClass( 'mw-editfooter-toggler-collapsed' );
            mw.storage.set( storeKey, expandedVal );
        } );

        $list.on( 'beforeCollapse.mw-collapsible', function () {
            $toggler.addClass( 'mw-editfooter-toggler-collapsed' );
            mw.storage.set( storeKey, collapsedVal );
        } );
    };

    mw.hook( 'wikipage.editform' ).add( function ( $editForm ) {
        var i;
        for ( i = 0; i < collapsibleLists.length; i++ ) {
            // Pass to a function for iteration-local variables
            handleOne(
                $editForm.find( collapsibleLists[ i ].listSel ),
                $editForm.find( collapsibleLists[ i ].togglerSel ),
                collapsibleLists[ i ].storeKey
            );
        }
    } );
}() );