@exadel/esl/modules/esl-media/core/esl-media-iobserver.js

Exadel Smart Library (ESL) is the lightweight custom elements library that provide a set of super-flexible components

let iObserver;
/** ESL Media Play-In-Viewport IntersectionObserver instance */
export function getIObserver(lazy = false) {
    if (!iObserver && !lazy) {
        iObserver = new IntersectionObserver(function (entries) {
            entries.forEach(handleViewport);
        }, {
            threshold: [0.05, 0.1, 0.25, 0.33, 0.5, 0.66, 0.75, 0.9, 1]
        });
    }
    return iObserver;
}
function handleViewport(entry) {
    const video = entry.target;
    const root = entry.rootBounds || {
        width: Number.POSITIVE_INFINITY,
        height: Number.POSITIVE_INFINITY
    };
    const rect = entry.intersectionRect;
    const ratio = Math.max((rect.width * rect.height) / (root.width * root.height), entry.intersectionRatio);
    // Removes `lazy` attribute when media is in the viewport with min ratio RATIO_TO_ACTIVATE
    if (entry.isIntersecting && ratio >= video.RATIO_TO_ACTIVATE && video.lazy === 'auto') {
        video.$$attr('lazy', false);
    }
    // Skip if video state management if feature is disabled
    if (!video.playInViewport)
        return;
    // Videos that playing and out of min ratio should be stopped
    if (video.active && ratio <= video.RATIO_TO_STOP) {
        video.pause(true);
    }
    // Videos that not playing and in min ratio to start should be started
    if (!video.active && ratio >= video.RATIO_TO_PLAY) {
        // Disallow for non autoplay-able videos or videos that was controlled by user
        if (!video.autoplay || video.isUserInitiated)
            return;
        video.play(video.canActivate(), true);
    }
}