Function getLowestCommonAncestor

docs/external/js/react-dom.development.js:8105–8143

* Return the lowest common ancestor of A and B, or null if they are in * different trees.

(instA, instB)

  function getLowestCommonAncestor(instA, instB) {
    var depthA = 0;

    for (var tempA = instA; tempA; tempA = getParent(tempA)) {
      depthA++;
    }

    var depthB = 0;

    for (var tempB = instB; tempB; tempB = getParent(tempB)) {
      depthB++;
    } // If A is deeper, crawl up.


    while (depthA - depthB > 0) {
      instA = getParent(instA);
      depthA--;
    } // If B is deeper, crawl up.


    while (depthB - depthA > 0) {
      instB = getParent(instB);
      depthB--;
    } // Walk in lockstep until we find a match.


    var depth = depthA;

    while (depth--) {
      if (instA === instB || instA === instB.alternate) {
        return instA;
      }

      instA = getParent(instA);
      instB = getParent(instB);
    }

    return null;
  }
  /**
   * Simulates the traversal of a two-phase, capture/bubble event dispatch.
   */