How to Intercept Page Navigation Using the onbeforeunload Event Handler in JavaScript?

Intercepting Page Navigation in JavaScript

In scenarios where it's crucial to prevent users from navigating away from a specific webpage, JavaScript provides reliable methods to control the navigation process. One such method is the onbeforeunload event handler.

onbeforeunload Event Handler

The onbeforeunload event is triggered right before the page is about to unload. Unlike the onunload event, which occurs after the page has started unloading, onbeforeunload gives you the opportunity to interrupt the navigation process.

Implementing onbeforeunload

To prevent navigation away from a webpage using onbeforeunload, follow these steps:

1. Define an event listener for the onbeforeunload event:

<code class="javascript">window.onbeforeunload = function() {
  // ...
};</code>

2. Inside the event listener, return a non-empty string to prevent navigation. If an empty string is returned, the browser will display a default message.

Example:

<code class="javascript">window.onbeforeunload = function() {
  return "";
};</code>

Note: For older browsers, you can customize the message displayed in the navigation confirmation prompt by returning a specific string:

<code class="javascript">window.onbeforeunload = function() {
  return "Are you sure you want to navigate away?";
};</code>

By utilizing the onbeforeunload event handler, you can effectively intercept page navigation and prompt users to confirm or cancel their actions before leaving the current webpage.

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