Default placeholder in text box prompt

[Calyps0]

Since CA 11 release, the new method for inserting custom Javascript (on reports with full interactivity set to yes) is now contained in universal js files which are saved on the server.  I'm trying to code around a Text Box prompt and insert some sort of placeholder text that disappears on click with the new custom controls.  Something like this:

https://www.w3schools.com/jsref/tryit.asp?filename=tryjsref_text_placeholder

I'm not a very savvy scripting person.  Has anyone been able to figure something like this out?

Thank you!