block8.ts

mounted() {
  this.progressStartMarker = document.querySelector<HTMLElement>('#progress-marker-start')
  this.progressEndMarker = document.querySelector<HTMLElement>('#progress-marker-end')

  if (!this.progressStartMarker || !this.progressEndMarker) {
    throw Error('Progress markers not found')
  }

  window.addEventListener('scroll', () => {
    this.getScrollPercentage(this.progressStartMarker!, this.progressEndMarker!)
  })
}