With that, we can initialize doubly linked list nodes easily by calling new DLinkedNode(key, value, null, null).
In the Cache class, we'll also want to add the standard addNode and removeNode helper methods, as we'll be doing that quite a bit. addNode specifically adds a new node to the head of the doubly linked list. removeNode removes it place by manipulating the pre and next values of its neighbors.
1class DLinkedNode {
2 constructor(key, val, pre, next) {
3 this.key = key;
4 this.val = val;
5 this.pre = pre;
6 this.next = next;
7 }
8}
9
10// for our Cache class
11addNode(node) {
12 node.pre = this.head;
13 node.next = this.head.next;
14 this.head.next.pre = node;
15 this.head.next = node;
16};
17
18removeNode(node) {
19 // take a node's predecessor
20 const pre = node.pre;
21 // find the node after it
22 const next = node.next;
23 // assign the predecessor's "next" node as the one after current
24 pre.next = next;
25 next.pre = pre;
26};