<body style="height: 5000px">
<script>
function snap(destination) {
if (Math.abs(destination - window.scrollY) < 3) {
scrollTo(window.scrollX, destination);
} else if (Math.abs(destination - window.scrollY) < 200) {
scrollTo(window.scrollX, window.scrollY + ((destination - window.scrollY) / 2));
setTimeout(snap, 20, destination);
}
}
var timeoutId = null;
addEventListener("scroll", function() {
if (timeoutId) clearTimeout(timeoutId);
timeoutId = setTimeout(snap, 200, parseInt(document.getElementById('snaptarget').style.top));
}, true);
</script>
<div id="snaptarget" class="snaptarget" style="position: relative; top: 200px; width: 100%; height: 200px; background-color: green"></div>
</body>