How to include FancyBox to the previously received HTML code when executing this script?

Question

JavaScript

There is such an example: here
Here is the main html code (let's call it PRIMARY) which is further processed using FancyBox. and when the script is executed, a new HTML is generated (let's call it SECONDARY) which is added to the end of the page and it is it that is already shown to the user.

I tried to immediately give the user a SECONDARY html code, but I can’t run FancyBox to the generated html code , my attempt , how to apply the FancyBox execution to the html code that was already received earlier?