wikimedia/mediawiki-extensions-Translate

( function () {
    'use strict';

    mw.translate = mw.translate || {};

    /**
     * Simple wrapper for storing recent groups for an user.
     *
     * @internal
     * @class mw.translate.recentGroups
     * @singleton
     * @since 2016.03
     */
    mw.translate.recentGroups = {
        get: function () {
            return JSON.parse( mw.storage.get( 'translate-recentgroups' ) ) || [];
        },

        append: function ( value ) {
            var items = this.get();

            items.unshift( value );
            items = items.filter( function ( item, index, array ) {
                return array.indexOf( item ) === index;
            } );
            items = items.slice( 0, 5 );

            mw.storage.set( 'translate-recentgroups', JSON.stringify( items ) );
        }
    };
}() );