JSFiddle - React, Tailwind, and code Playground

JavaScript

var A={B:{}};

function def(a,b,c,d){
 c=b.split('.');
 d=c.shift();
 a[d]||(a[d]={});
 !(c.length>0)||def(a[d],c.join('.'));
}
def(A,'B.C.D.E.F')
def(A,'B.C.D.EE.F')
def(A,'B.C.D.EE.F')
console.log(A);