Run the following code when the js page is loading
window.onbeforeunload = function(){
return "Unsaved content may be lost";
};
This code will not display the return value in Firefox and IE in Google This text is displayed under the browser.
Failure control
triggers js to run as follows:
window.onbeforeunload = function(){};
![[Web front-end] Node.js quick start](https://img.php.cn/upload/course/000/000/067/662b5d34ba7c0227.png)
