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/*
* Copyright (C) 2019-2020 Yomichan Authors
*
* 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();
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