In the same way that you can add custom HTML to a calendar title, footer, or event, you can add custom JavaScript as well. Just make sure to wrap your code in between some <script> and </script> tags.

In this extremely annoying example, here is how to make a calendar display a JavaScript alert box every time the page is loaded.

Step 1: Copy the Code

The JavaScript for this example is below:

<script>alert("Greetings, visitor!");</script>

Step 2: Paste the code

For this exercise, we paste it into the calendar Title.

The Title and Footer fields don't let you paste multi-line text. You might need to paste your JavaScript someplace else (like Notepad) first and remove the line breaks before pasting it into localendar.

Success!

This is a simple example, but there are almost limitless applications for using your own JavaScript (usage tracking, advanced UI customizations, browser detection, Google Analytics tracking, etc.)