HTML + Javascript: Dynamic Image Resize?

I am trying to get some JavaScript to programmatically adjust a HTML img tag's width to display various sized images correctly.

I have a fixed width img tag at 800px to display an image, this is the max width.

If the image is wider then 800px I want to display it at 800px wide;

If the image is less than 800px wide I want to preserve its width to avoid stretching it.

I use this html/javacript code to get a partial solution:

function resize_image(id) {
	var img = document.getElementById(id);
	var normal_width = img.width;
	img.removeAttribute("width");
	var real_width = img.width;
	if (real_width < normal_width) {
		img.width = real_width;
	} else {
		img.width = normal_width;
	}
}

<img id="myimage" onload="resize_image(self.id);" src="https://via.placeholder.com/350x150" width="800" />

The above code seems to work on all browsers I have tested except Safari (images don't display unless you refresh the page).

I know I can use CSS max-width but that wont work on IE < 7 which is a show stopper.

How can I get this working for all browsers? Many thanks in advance.

I have never seen a safari in work, but you can try changing your onload event to this:

onload="resize_image(self.id);return true"

It could be that without a return value, safari thinks that this object should not be loaded.