Is In Viewport Detection With IntersectionObserver API

This is a tiny example that shows how to detect if an element is in the viewport using the Intersection Observer API.

How to use it:

1. The main function for ‘is in viewport’ detection.

function inViewport(elem, callback, options = {}) {
  return new IntersectionObserver(entries => {
    entries.forEach(entry => callback(entry));
  }, options).observe(document.querySelector(elem));
}

2. Attach the function to the target element and determine the parent container.

<div class="box">
  <div class="scroll">
    <div>
      <div class="target">Target</div>
    </div>
  </div>
  <span>In viewport: <strong>false</strong></span>
</div>

inViewport('.target', element => {
  // returns true or false
}, {
  root: document.querySelector('.scroll')
})