after getting the whole dom of a element in js how can i get the width of that DOM code example

Example: get element size javascript

// Get Content + Padding + Border
let box = document.querySelector('div');
let width = box.offsetWidth;
let height = box.offsetHeight;

// Get Content + Padding only
let box = document.querySelector('div');
let width = box.clientWidth;
let height = box.clientHeight;