How to fix the issue of beforeunload event not being executed?

If the beforeunload event does not execute, it could be because you are using asynchronous operations or preventing the default behavior in the event handler. Here are some possible solutions:

1. Avoid using asynchronous operations: ensure that no asynchronous operations, such as setTimeout or Promise, are used in the beforeunload event handler. This is because the page may already be unable to maintain an active state when this event is triggered.
2. Ensure not to block the default behavior: Do not call the preventDefault() method in the beforeunload event handler. If preventDefault() is called, the browser may ignore your handler and close the page directly.
3. Bind event handlers as early as possible: On page load, make sure to bind the beforeunload event handler early to ensure it can be executed when needed. You can use the addEventListener() method to bind event handlers, for example:

window.addEventListener('beforeunload', function(event) {
  // 在这里执行您的代码
});

1. Utilizing a return value: When a string is returned in the event handler, the browser will display it as a prompt message to ask users if they want to leave the page. For example:

window.addEventListener('beforeunload', function(event) {
  event.returnValue = '您确定要离开此页面吗？';
});

Please note that different browsers may handle the beforeunload event differently, and these methods may be ineffective in some browsers. For specific needs, you may need to use other techniques such as using the JavaScript unload event or implementing callback functions to perform relevant actions.