Get the absolute width of an element.

get_absolute_width.js

const getAbsoluteWidth = (element) => {
  const style = window.getComputedStyle(element);
  const attrs = ['width', 'padding-left', 'padding-right', 'margin-left', 'margin-right'];
  
  return attrs
    .map((k) => parseInt(style.getPropertyValue(k), 10))
    .reduce((p, c) => p + c);
};