Checks if window has been zoomed.

window-zoom.js

// modified from https://stackoverflow.com/a/52008131/1461204
const zoomEvent = new Event('zoom')
let currentRatio = window.devicePixelRatio

function checkZooming() {
  if (currentRatio !== window.devicePixelRatio) {
    window.dispatchEvent(zoomEvent)
  }
}

window.addEventListener('resize', checkZooming)

// usage
window.addEventListener('zoom', () => {
  console.log('zoomed!')
})

Be aware that https://developer.mozilla.org/en-US/docs/Web/API/ResizeObserver is not compatible with Safari and IE

It is now