You could use whitelist to save your function(s) name. If I right understand what do you want.

Suppose I have a file with

function eventCapture(){
// Some logic that I want obfuscated here
return result
}

Then I have another file that will be calling eventCatpure. This second file cannot be obfuscated.

div.onclick = eventCapture

How can I obfuscate the body of the eventCapture function, so that I can reference it as above?