How to get height of entire document with JavaScript?

Question

Some documents I can\'t get the height of the document (to position something absolutely at the very bottom). Additionally, a padding-bottom on seems to do nothing on these

Answer 1

The proper answer for 2017 is:

document.documentElement.getBoundingClientRect().height

Unlike document.body.scrollHeight this method accounts for body margins. It also gives fractional height value, which can be useful in some cases