How can I get the browser's scrollbar sizes?

Question

How can I determine the height of a horizontal scrollbar, or the width of a vertical one, in JavaScript?

Answer 1

Create an empty div and make sure it's present on all pages (i.e. by putting it in the header template).

Give it this styling:

#scrollbar-helper {
    // Hide it beyond the borders of the browser
    position: absolute;
    top: -100%;

    // Make sure the scrollbar is always visible
    overflow: scroll;
}

Then simply check for the size of #scrollbar-helper with Javascript:

var scrollbarWidth = document.getElementById('scrollbar-helper').offsetWidth;
var scrollbarHeight = document.getElementById('scrollbar-helper').offsetHeight;

No need to calculate anything, as this div will always have the width and height of the scrollbar.

The only downside is that there will be an empty div in your templates.. But on the other hand, your Javascript files will be cleaner, as this only takes 1 or 2 lines of code.