I need to send an email from my sheets. How do I get the cell values as variables in HTML?

I am working on a code that reads the sheets and copies the whole template to an email. I am using all google tools and apps script. The problem I am facing right now is that I don’t how to link the variables I declared in the java script code with the cells values into the html file where I need the values to be displayed. Can someone please explain me and give me an example if possible. I looked at other codes available here but they don’t have the link/connection between java and html.

Thanks