How can I implement a pop-up that activates when a reader tries to close the browser tab or window using JavaScript in Webflow?

To implement a pop-up that activates when a reader tries to close the browser tab or window in Webflow using JavaScript, you can use the `beforeunload` event.

Here's an example code snippet that demonstrates how to achieve this:

In the Webflow Designer, go to the page where you want to implement the pop-up.

1. Add a new HTML embed element to the page by clicking on the "+" button in the Designer toolbar.
2. In the HTML embed element, write the following code:

```html

```

3. Customize the code within the event listener to display your desired pop-up or message. You can use any method available in Webflow, such as a hidden modal that becomes visible or an alert box.
4. Save the changes and publish your site.

Now, when a reader tries to close the browser tab or window, the pop-up will be activated, displaying your custom message. The reader will have the option to stay on the page or leave, depending on their choice.

Please note that browser restrictions may limit the ability to customize the pop-up or message further. Some browsers may display a default message instead, and users might have the option to disable the pop-up entirely through their browser settings.

It's important to consider the user experience and not abuse this functionality to trap users on your website against their will.