How to display alert message when closing window/tab using jQuery

What Will I Learn?

You will learn how to use jQuery
You will learn on beforeunload function
You will learn how to display message before closing tab/window

Requirements

Basic knowledge about HTML
Basic knowledge about JavaScript
You have to install or host the jQuery file, You can add jQuery CDN if you don't want to install or host it

Difficulty

Basic

Tutorial Contents

This alert message usually use in page that contain a form, When you try to close the page or tab/window while the form not fill completely will alert the message to confirm are you sure to close the tab. jQuery has provided on beforeload event to display the confirm message before closing the tab. For more detail lets pay attention on steps bellow :

&Creating Sample Form

Open your Text editor
Create new file save as alert.html
Add the HTML element as usual.

<html>
<head>
<title>Display alert before closing page</title>
</head>
<body>
</body>
</html>

Create a sample inpt form

<form>
    <h2>Sample FORM</h2>
     Name: <input type="text"><br><br>
     Class: <input type="text">
  </form>

&Adding jQuery CDN

As we know, to use jQuery we need to install or host it. Or we can also add jQuery CDN if we don't want to install or host it. we also have many choices CDN that we can use, either Google CDN or Microsoft CDN. For more Detail you can visit jquery official web. In this tutorial I use Google CDN. Add the CDN in <head> element.

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>

&Adding jQuery Script

To write the jQuery Script we should open <script> tag. You can put it in <head>or element.

<script></script>

Before add more event in jQuery. There is an event that we should add for the first. It is ready() event. this event to make sure that all html elements are loaded. if it is, then it will load jQuery script. So, all jQuery Script must write in this function event.

$(document).ready(function(){
});

Select the window.

$(window)

Then Add on beforeunload event function

$(window).on('beforeunload',function(){
});

To display auto alert message we just need return '' in previous function like this

$(window).on('beforeunload',function(){
      return '';
    });

&Testing

Save the file try to run on your browser
Try to write something on input form
Then try to close the tab, you will see the confirm message before closing
The last try to reload the page, you will also get the confirm alert before reloading

Finish, For the full code you can copy bellow:

<html>
<head>
    <title>Display alert before closing page</title>
    <script src="https://code.jquery.com/jquery-1.12.4.js"></script>  
    <script>
  $(document).ready(function(){
    $(window).on('beforeunload',function(){
      return '';
    });
  });
  </script>
</head>
<body>
  <form>
    <h2>Sample FORM</h2>
     Name: <input type="text"><br><br>
     Class: <input type="text">
  </form> 
</body>
</html>

LIVE DEMO

Curriculum

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