getVisibleRect(el)
Note: tests are failing, because they only run in PhantomJS on travis for now - enabling real browsers soon.
When the element is inside the viewport, getVisibleRect() returns:
{
visibleHeight,
visibleWidth,
height,
width,
// these positions are relative to the elements top/left
top,
bottom,
left,
right
}
When element is outside the viewport, visibleHeight and visibleWidth will be 0,
while top/bottom/left/right will be undefined.
My primary purpose for building this (and not using something else) is to calculate the visible percentage of the
element. visibleHeight is actually bottom - top and visibleWidth is right - left. This means that the visible
percentage is (visibleHeight * visibleWidth) / (height * width).