The most commonly used JavaScript effect on the Web is the image rollover. For the one person with access to the Web who’s never seen one before, an image rollover happens when you move your ...

Image() object in JavaScript and pass it the URL of the image you want preloaded. Say we have an image called heavyimagefile.jpg, which we want to ... just one image; for example, ...

The image probably isn't loaded by that time. I mean, it's probably a couple milliseconds, if that, between when you assign that src and when you ask for the width and height.