xpath.js

function getXpath(element) {
  if(!element || !element.parentNode) return ''
  let xpath = getXpath(element.parentNode) + '/' + element.tagName
  const elements = []
  for(const e of element.parentNode.childNodes) {
    if(e.tagName == element.tagName) elements.push(e)
  }
  if(1 < elements.length) {
    const i = elements.indexOf(element)
    xpath += '[' + (i+1) + ']'
  }
  return xpath.toLowerCase()
}

function getXpathRec(element, childPath = '') {
  if(!element || !element.parentNode) return childPath.toLowerCase()
  const elements = [...element.parentNode.childNodes].filter(e => e.tagName == element.tagName)
  const xpath = '/' + element.tagName + (1 < elements.length ? `[${elements.indexOf(element) + 1}]` : '')
  return getXpathRec(element.parentNode, xpath + childPath)
}