Visualize .getBoundingClientRect()

draw-rect.js

function draw(rect) {
  const div = document.createElement("div");
  // Might be needed on crazy pages, but makes the console output for the div crazy large.
  // div.style.all = "unset";
  div.style.position = "absolute";
  div.style.zIndex = "2147483647";
  // At least _try_ to scroll along. Won’t work for inner scroll.
  div.style.left = `${window.scrollX + rect.left}px`;
  div.style.top = `${window.scrollY + rect.top}px`;
  div.style.width = `${rect.width}px`;
  div.style.height = `${rect.height}px`;
  div.style.boxSizing = "border-box";
  div.style.border = "1px solid magenta";
  div.style.pointerEvents = "none";
  document.documentElement.append(div);
  return div;
}