Is element in view (jquery)

elementinview.js

function isElementInViewport(el)
{
    if (typeof jQuery === 'function' && el instanceof jQuery)
    {
        el = el[0];
    }
    
    var rect = el.getBoundingClientRect();
    
    return (
        rect.top >= 0 &&
        rect.left >= 0 &&
        rect.bottom <= $(window).height() &&
        rect.right <= $(window).width()
    );
}