The clientHeight read-only property of the Element interface is zero for elements with no CSS or inline layout boxes; otherwise, it's the inner height of an element in pixels. It includes padding but excludes borders, margins, and horizontal scrollbars (if present).
clientHeight can be calculated as: CSS height + CSS padding - height of horizontal scrollbar (if present).
When clientHeight is used on the root element (the <html> element), (or on <body> if the document is in quirks mode), the viewport's height (excluding any scrollbar) is returned.
An integer.