source/sortable-item-handle.js
function isParent(possibleParent, elem) {
    if(!elem || elem.nodeName === 'HTML') {
      return false;
    }

    if(elem.parentNode === possibleParent) {
      return true;
    }

    return isParent(possibleParent, elem.parentNode);
  }
function isParent(possibleParent, elem) {
    if(!elem || elem.nodeName === 'HTML') {
      return false;
    }

    if(elem.parentNode === possibleParent) {
      return true;
    }

    return isParent(possibleParent, elem.parentNode);
  }
function isParent ( possibleParent , elem ) { if ( ! elem || elem . nodeName === 'HTML' ) { return false ; } if ( elem . parentNode === possibleParent ) { return true ; } return isParent ( possibleParent , elem . parentNode ) ; }
Check if a node is parent to another node
Check if a node is parent to another node