/* * Copyright (C) 2019-2020 Alex Yatskov <alex@foosoft.net> * Author: Alex Yatskov <alex@foosoft.net> * * This program is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, either version 3 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program. If not, see <https://www.gnu.org/licenses/>. */ class PageExitPrevention { constructor() { } start() { PageExitPrevention._addInstance(this); } end() { PageExitPrevention._removeInstance(this); } static _addInstance(instance) { const size = PageExitPrevention._instances.size; PageExitPrevention._instances.set(instance, true); if (size === 0) { window.addEventListener('beforeunload', PageExitPrevention._onBeforeUnload); } } static _removeInstance(instance) { if ( PageExitPrevention._instances.delete(instance) && PageExitPrevention._instances.size === 0 ) { window.removeEventListener('beforeunload', PageExitPrevention._onBeforeUnload); } } static _onBeforeUnload(e) { if (PageExitPrevention._instances.size === 0) { return; } e.preventDefault(); e.returnValue = ''; return ''; } } PageExitPrevention._instances = new Map();