HTML5 and Javascript to play videos only when visible

Question

I am interested in setting up an HTML page with multiple video clips such that each video clip plays only while visible and then pauses when out of view.

I have fo

Answer 1

OK, I think, it must be something like this:

var videos = document.getElementsByTagName("video");

function checkScroll() {
    var fraction = 0.8; // Play when 80% of the player is visible.

    for(var i = 0; i < videos.length; i++) {

        var video = videos[i];

        var x = video.offsetLeft, y = video.offsetTop, w = video.offsetWidth, h = video.offsetHeight, r = x + w, //right
            b = y + h, //bottom
            visibleX, visibleY, visible;

            visibleX = Math.max(0, Math.min(w, window.pageXOffset + window.innerWidth - x, r - window.pageXOffset));
            visibleY = Math.max(0, Math.min(h, window.pageYOffset + window.innerHeight - y, b - window.pageYOffset));

            visible = visibleX * visibleY / (w * h);

            if (visible > fraction) {
                video.play();
            } else {
                video.pause();
            }

    }

}

window.addEventListener('scroll', checkScroll, false);
window.addEventListener('resize', checkScroll, false);