后序遍历（后跟次序遍历）

先打印左边的，再打印右边的，再打印当前的

  1. class Node{
  2.     constructor(value) {
  3.         this.value = value;
  4.         this.left = null;
  5.         this.right = null;
  6.     }
  7. }
  10. let a = new Node("a");
  11. let b = new Node("b")
  12. let c = new Node("c")
  13. let d = new Node("d")
  14. let e = new Node("e")
  15. let f = new Node("f")
  16. let g = new Node("g")
  18. a.left = c
  19. a.right = b
  21. c.left = f
  22. c.right = g
  24. b.left = d
  25. b.right = e
  27. function fl(root){
  28.     if(root == undefined) return;
  29.     fl(root.left)
  30.     fl(root.right)
  31.     console.log(root.value)
  32. }
  34. fl(a)