getUniquePath(document.querySelector('img')) => html>body>div>div>div>div:nth-child(2)>table>tbody>tr>th:nth-child(2)>div>img

uniqueElementPath.js

function getUniquePath(element){
  if(element.nodeType !== Node.ELEMENT_NODE){
    throw new Error('element must be element node')
  }
  if(element.id){
    return '#' + element.id
  }
  var path = ''
  while(element){
    var name = element.localName
    if(!name){
      break;
    }
    var parent = element.parentNode
    if(parent){
      var nodeList = parent.childNodes,
          node,
          idx = 0
      for(var i = 0; i < nodeList.length; i++){
        node = nodeList[i]
        if(node.localName === name){
          idx += 1
        }
        if(node === element){
          break
        }
      }
      if(idx > 1){
        name += ':nth-child(' + idx + ')';
      }
    }
    path = name + (path ? '>' + path : '');
    element = parent
  }
  return path
}