<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <title>window sizes</title> <script> function updateText(elem) { var size = window.innerWidth + "/" + window.innerHeight; document.getElementById(elem).textContent = size; console.log(elem + " window size: " + size); } document.addEventListener("DOMContentLoaded", function() { updateText("hidden"); console.log("loaded"); }); </script> </head> <body> <p>visible: <span id="visible">unknown</span></p> <p>hidden: <span id="hidden">unknown</span></p> </body> </html>