access_ref_elements.js

// get current element ref
  const ref = useRef(null)

  // persist index
  let sectionIndex: number

  // helper to get element index from the DOM
  const getElementIndex = () => {
    // if (sectionIndex) {
    //   console.log({ sectionIndex })
    //   return sectionIndex
    // }

    // TODO: give credits
    // https://stackoverflow.com/a/11762035
    // get nodes from j-scroll container
    const nodes = Array.prototype.slice.call(
      document.getElementById(`j-scroll-container`)?.children || {}
    )

    const index = nodes.indexOf(ref.current)

    if (index > 0) {
      sectionIndex = index
    }

    // return index
    return sectionIndex
  }