Detect if an element is visible (without using jQuery)

Question

I\'m trying to detect if an html element I gave an id is visible or not without using jquery.

The context:

In the forgotten user password page,

Answer 1

Google helped me finding out how jQuery does it, you can do the same:

In jQuery 1.3.2 an element is visible if its browser-reported offsetWidth or offsetHeight is greater than 0.

Release notes

Searching the source code gave me this:

// The way jQuery detect hidden elements, and the isVisible just adds "!".
elem.offsetWidth === 0 && elem.offsetHeight === 0