How can the dropbox and the integer property effect something?

[#1]

Hello,

I have created a custom dropbox property in my extension.

I want to change the font-family depending on my selection in the dropdown menu.

I have the same problem with the font-size.

Therefor I have created a custom integer property.

How can i implement a function in my .js file that makes the selections effect something?

Thank you in advance!

Florian