element is in viewport?

is-in-viewport.coffee

'use strict'

# http://stackoverflow.com/a/7557433
# https://gist.github.com/anonymous/f09b5cd487b5ad55c46e
module.exports = (element, partial = false, position = 0.85)->
    rect = element.getBoundingClientRect()
    windowHeight = window.innerHeight or document.documentElement.clientHeight
    windowWidth = window.innerWidth or document.documentElement.clientWidth
    unless partial
        rect.top >= 0 and
            rect.left >= 0 and
            rect.bottom <= windowHeight and
            rect.right <= windowWidth
    else
        rect.left >= 0 and rect.right <= windowWidth and
            ((rect.top >= 0 and rect.top <= windowHeight * position) or
                (rect.bottom >= windowHeight * (1 - position) and rect.bottom <= windowHeight))