Javascript on plone page

Hello, I would like to know how can I call a javascript function in a post on the "Page" plugin in Plone?

What is your specific use case?

I wanted to do as shown in the attached image.
I found this example on the internet but I do not know how to do it, I needed to know what add-on they are using to do it this way.
Would you help me?

Either write your custom browser view with a customized rendering template or inject your own Javascript code using Diazo.

Ok thank you!