Detecting when user scrolls to bottom of div with React js

Question

I have a website with different sections. I am using segment.io to track different actions on the page. How can I detect if a user has scrolled to the bottom of a div? I have tried the following but it seems to be triggered as soon as I scroll on the page and not when I reached the bottom of the div.

componentDidMount() {
  document.addEventListener('scroll', this.trackScrolling);
}

trackScrolling = () => {
  const wrappedElement = document.getElementById('header');
  if (wrappedElement.scrollHeight - wrappedElement.scrollTop === wrappedElement.clientHeight) {
    console.log('header bottom reached');
    document.removeEventListener('scroll', this.trackScrolling);
  }
};

Answer 1

you can use el.getBoundingClientRect().bottom to check if the bottom has been viewed

isBottom(el) {
  return el.getBoundingClientRect().bottom <= window.innerHeight;
}

componentDidMount() {
  document.addEventListener('scroll', this.trackScrolling);
}

componentWillUnmount() {
  document.removeEventListener('scroll', this.trackScrolling);
}

trackScrolling = () => {
  const wrappedElement = document.getElementById('header');
  if (this.isBottom(wrappedElement)) {
    console.log('header bottom reached');
    document.removeEventListener('scroll', this.trackScrolling);
  }
};