Intersection observer – How do you remove a class after leaving the view port

I am adding a class when a div gets into the viewport using Intersection Observer. I just can’t figure out how to remove the class when the div leaves the viewport. This is what I have so far:

const callback = function (entries) {
    entries.forEach(entry => {
        if(entry.isIntersecting)
        {
            entry.target.classList.add('animate1');
          observer.unobserve(entry.target)
          }
    });
}
const observer = new IntersectionObserver(callback);
const targets = document.querySelectorAll('.overlay');
targets.forEach(target => {
    observer.observe(target);
})