window.addEventListener('scroll', function (event) {
if (isInViewport(theElementToWatch)) {
// update the element display
}
}, false);
function isInViewPort(element) {
// Get the bounding client rectangle position in the viewport
var bounding = element.getBoundingClientRect();
// Checking part. Here the code checks if it's *fully* visible
// Edit this part if you just want a partial visibility
if (
bounding.top >= 0 &&
bounding.left >= 0 &&
bounding.right <= (window.innerWidth || document.documentElement.clientWidth) &&
bounding.bottom <= (window.innerHeight || document.documentElement.clientHeight)
) {
console.log('In the viewport! :)');
return true;
} else {
console.log('Not in the viewport. :(');
return false;
}
}