MRU in JavaScript using Doubly linked list

mru-using-doubly-linked-list.js

class Node {
    constructor(value) {
        this.prev = null;
        this.next = null;
        this.value = value;
    }
}

class MRU {
  constructor(size) {
      this.size = size;
      this.head = null;
      this.tail = null;
      this.map = new Map();
  }

  add(value) {
      const node = new Node(value);
      node.next = this.head;
      this.head = node;

      if (this.head.next) {
          this.head.next.prev = this.head;
      }

      if (this.tail == null) {
          this.tail = node;
      } else if (this.tail.prev == null) {
          this.tail.prev = node;
      }

      this.map.set(value, node);
      
      return this.head;
  }

  remove(node) {
      if (node === this.head) {
          this.head = node.next;
          node.next.prev = null;
          node.next = null;
      } else if (node === this.tail) {
          this.tail = this.tail.prev;
          this.tail.next = null;
          node.prev = null;
      } else {
          node.prev.next = node.next;
          node.next.prev = node.prev;
          node.prev = node.next = null;
      }

      this.map.delete(node.value);

      return node;
  }

  put(value) {
    if (this.map.has(value)) {
       if (this.size !== 1) {
            this.remove(this.map.get(value));
            return this.add(value);
       }
    } else {
      if (this.map.size === this.size) {
        this.remove(this.tail);
      }

      return this.add(value);
    }
  }

  list() {
      const a = [];
      let n = this.head;

      while (n) {
          a.push(n.value);
          n = n.next;
      }

      return a;
  }
}

const c = new MRU(3);

console.clear();
c.put(1);
console.debug(c.list());
c.put(2);
console.debug(c.list());
c.put(3);
console.debug(c.list());
c.put(4);
console.debug(c.list());
c.put(5);
console.debug(c.list());
c.put(4);
console.debug(c.list());
c.put(3);
console.debug(c.list());
c.put(6);
console.debug(c.list());

// Space complexity: O(n)
// Time complexity: put-O(1),list-O(n)