I have a datatable inside a bootstrap modal. I am able to add/update/delete individual rows. But I am not able to clear all the rows. It does nothing.

I am using MySQL to sum data then display it in datatable but since database is bigger it became very slow I am trying a new approach where I use client side to do calculation, tried every code I could find but keep getting this error :

i want to perform these tasks on datatable Initialization