document.body.scrollTop Firefox returns 0 : ONLY JS

Question

Any alternatives in pure javascript?

The following works in opera, chrome and safari. Have not tested yet on explorer:

http://monkey-me.herokuapp.com

Answer 1

Instead of using IF conditions, there's easier way to get proper result by using something like this logical expression.

var bodyScrollTop = document.documentElement.scrollTop || document.body.scrollTop;

Both parts return zero by default so when your scroll is at zero position this will return zero as expected.

bodyScrollTop = 0 || 0 = 0

On page-scroll one of those parts will return zero and another will return some number greater than zero. Zeroed value evaluates to false and then logical OR || will take another value as result (ex. your expected scrollTop is 300).

Firefox-like browsers will see this expression as

bodyScrollTop = 300 || 0 = 300

and rest of browsers see

bodyScrollTop = 0 || 300 = 300

which again gives same and correct result.

In fact, it's all about something || nothing = something :)