src/js/base/core/dom.js
function isLeftEdgeOf(node, ancestor) {
  while (node && node !== ancestor) {
    if (position(node) !== 0) {
      return false;
    }
    node = node.parentNode;
  }

  return true;
}
function isLeftEdgeOf(node, ancestor) {
  while (node && node !== ancestor) {
    if (position(node) !== 0) {
      return false;
    }
    node = node.parentNode;
  }

  return true;
}
function isLeftEdgeOf ( node , ancestor ) { while ( node && node !== ancestor ) { if ( position ( node ) !== 0 ) { return false ; } node = node . parentNode ; } return true ; }
returns whether node is left edge of ancestor or not.

@param {Node} node
@param {Node} ancestor
@return {Boolean}
returns whether node is left edge of ancestor or not .