61 lines
1.7 KiB
JavaScript
61 lines
1.7 KiB
JavaScript
/*
|
|
* 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();
|