1. var getIntersectionNode = function(headA, headB) {
    2.     let lastHeadA = null;
    3.     let lastHeadB = null;
    4.     let originHeadA = headA;
    5.     let originHeadB = headB;
    6.     if (!headA || !headB) {
    7.         return null;
    8.     }
    9.     while (true) {
    10.         if (headB == headA) {
    11.             return headB;
    12.         }
    13.         if (headA && headA.next == null) {
    14.             lastHeadA = headA;
    15.             headA = originHeadB;
    16.         } else {
    17.             headA = headA.next;
    18.         }
    19.         if (headB && headB.next == null) {
    20.             lastHeadB = headB
    21.             headB = originHeadA;
    22.         } else {
    23.             headB = headB.next;
    24.         }
    25.         if (lastHeadA && lastHeadB && lastHeadA != lastHeadB) {
    26.             return null;
    27.         }
    28.     }
    29.     return null;
    30. };