Detect when elements within a scrollable div are out of view

Question

I need to find a good solution to the following problem. I see a lot of people asking about tracking if an element is in or outside of view Port for the page or browser wind

Answer 1

Based of the best answer. Instead of just telling you if an element is partially visible or not. I added a little extra so you can pass in a percentage (0-100) that tells you if the element is more than x% visible.

function (container, element, partial) {
    var cTop = container.scrollTop;
    var cBottom = cTop + container.clientHeight;
    var eTop = element.offsetTop;
    var eBottom = eTop + element.clientHeight;
    var isTotal = (eTop >= cTop && eBottom <= cBottom);
    var isPartial;

    if (partial === true) {
        isPartial = (eTop < cTop && eBottom > cTop) || (eBottom > cBottom && eTop < cBottom);
    } else if(typeof partial === "number"){
        if (eTop < cTop && eBottom > cTop) {
            isPartial = ((eBottom - cTop) * 100) / element.clientHeight > partial;
        } else if (eBottom > cBottom && eTop < cBottom){ 
            isPartial = ((cBottom - eTop) * 100) / element.clientHeight > partial;
        }
    }
    return (isTotal || isPartial);
}