how can i call an function present in backend while clicking the button from frontend?

This is my button present in frontend

//
         <button /*onClick={say.stop()}*/ className='stopspeech'>Stop speaking</button> 

// 

and i want to call this say.stop() function with a click, and this say.stop() function is in my
backend.

so how can add a new endpoint in backend which call this function onclicking the button.
i want this in express.