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-rw-r--r--ext/bg/js/page-exit-prevention.js60
1 files changed, 60 insertions, 0 deletions
diff --git a/ext/bg/js/page-exit-prevention.js b/ext/bg/js/page-exit-prevention.js
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+++ b/ext/bg/js/page-exit-prevention.js
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+/*
+ * Copyright (C) 2019 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 <http://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();