lazy.ts

export const initLazyloading = (selector: string): void => {
    let images = document.querySelectorAll(selector)

    if ('IntersectionObserver' in window) {
        // Create new observer object
        let lazyImageObserver = new IntersectionObserver(function(entries, observer) {
            // Loop through IntersectionObserverEntry objects
            entries.forEach(function(entry) {
                // Do these if the target intersects with the root
                if (entry.isIntersecting) {
                    let lazyImage: any = entry.target
                    lazyImage.src = lazyImage.dataset.src
                    lazyImage.classList.remove('lazy')
                    lazyImage.classList.add('lazyloaded')
                    lazyImageObserver.unobserve(lazyImage)
                }
            })
        })

        // Loop through and observe each image
        images.forEach(function(lazyImage) {
            lazyImageObserver.observe(lazyImage)
        })
    }
}