How to set a Ajax URL so that I can use Jquery.post(URL)

Hi there, I need quick help for ajax. Let me clarify.
https://travisweihermuller.com/portfolio/
kindly visit this website. You will see there is an option to give a like. I want to create an exact similar thing on webflow, I found the way how it works and I have written the custom code the like amount is increased but when I reload the page it’s back to the previous state. Here is the custom code for that. Look both images
myajax
myajax2

The error says: “portfolio:262 Uncaught ReferenceError: myajax is not defined”
On their website they declare a URL into myajax variable

But in webflow how can i declare a ajax URL for that so that when I reload the page that page should show the increase value not the previous value.
Here is my webflow website link: Portfolio