How to determine actual viewport width and height on iOS
EDIT: Use document.body.clientWidth and document.body.clientHeight to get the calculations you desire, as my original solution is now considered obsolete.
You can use document.width and document.height
Here's a test on the old Space Jam site (which came to mind when trying to think of a site that definitely wouldn't be responsive).
Here's a trickier but kinda useless way:Make a page-sized element then compute/get its actual size.
let page_size = { height: null, width: null };{ let div = document.createElement('div'); (styles => Object.keys(styles).forEach(k => div.style[k] = styles[k]))({ height: '100vh', width: '100vw', position: 'fixed', top: '-100vh', left: '-100vw' }) document.body.appendChild(div); page_size.height = div.offsetHeight; page_size.width = div.offsetWidth;}