const images = document.querySelectorAll('img')
const callback = (entries) => {
entries.forEach(enter =>{
if(enter.isIntersectiing){
const image = enter.target;
const data_src = image.getAttribute('data_src')
image.setAttribute('src',data_src)
observer.unobserve(img)
}
})
}
const observer = new IntersectionObserver(callback)
images.forEach( image =>{
observer.observer(img)
})