Двусвязный список

1class DNode {
2  value: number
3  prev: DNode | null = null
4  next: DNode | null = null
5  constructor(value: number) { this.value = value }
6}
7 
8function insertAfter(node: DNode, value: number): DNode {
9  const fresh = new DNode(value)
10  fresh.prev = node
11  fresh.next = node.next
12  if (node.next !== null) node.next.prev = fresh
13  node.next = fresh
14  return fresh
15}
16 
17function removeNode(node: DNode): void {
18  if (node.prev !== null) node.prev.next = node.next
19  if (node.next !== null) node.next.prev = node.prev
20}