Bear Bibeault

The really weird thing about this in JavaScript, is that its value depends not on how the function is declared, but on how it is called.

This makes it unreliable in general functions because you can’t be sure exactly what it’s going to refer to. This is the principal reason that it is now gone from arrow functions.

For event handlers it is much better to rely upon the passsd event than the value of this, which won’t even exist if the handler is declared as an arrow function.

Piet Souris wrote:and then myFunction is a function without any parameter

Nope. All that's happening here is that a reference to the function is being passed. When the function is called, it will get passed the event argument as expected.

And, in the spirit of functional programming, arrow functions should be preferred over named functions, and then the wierdnesses around “this” go away.

See this article regarding proper structure of a Java web application.

I use VS Code for frontend development, and IntelliJ for backend.

That's not what a regular expression is intended for. What's wrong with good old comparisons?

For problems like this, and a score of other reasons, Java code in a JSP has been obsolete for over 20 years. 20 years. 2 decades.

Pleaser see this article for a description of how Java web applications should be structured.

Sounds like the most likely cause is that the script is executing before the DOM element identified by 'piechart_3d' exists.

Easiest fix would be to move the script to a script block that is placed after the DOM element.

Most correct fix would be to execute the code in an event handler that executes after the DOM is completely loaded.

Have you followed the instructions in the JSP FAQ for creating server-relative URLs that start with the context path?

If so, you'll need to show your work so we're not just guessing.

For the purposes of local storage there is no distinction; local storages persists across sessions/instances.

local storage survives browser session. session storage is per browser session.

My understanding is that OP is using local storage, not the local file system. But it's still not clear to me exactly what they're trying to accomplish or what the actual issue is...

Code should never go in a JSP page.

https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Disposition

If you need to save a formatted report, it's customary to have a backend process take the data and either generate a PDF-formatted report, a CSV-formatted report, or an HTML-formatted report (or options for any of the above). Setting the response headers properly makes the response a "download", which the users can then save wherever they please on their file systrm.