how to split acroos the string where neither index nor particular keyword is specfied

Input: plasticCup()
Output: plastic cup 

I have a task where i need to split acroos where i get the capital letter in javascript then make it small and then join them all as a word also need to remove the parantheses from them

example  Input: plasticCup()
example Output: plastic cup


example Input: sarangTry()
example Output sarang try