Implement An LRU Cache algorithm JavaScript

lru.js

const head = Symbol('head')
const tail = Symbol('tail')
class DoublyLinkedListNode {
    constructor(value, index=0) {
        this.value = value;
        this.previous = null;
        this.next = null;
        this.index = index;
    }
}
class DoublyLinkedListHashTable{  
    constructor() {
        this.nodes = new Map();
    } 
    add(key, val) {
       if(!this[head]) {
        this[head] = new DoublyLinkedListNode(val, key);
        this[tail] = this[head];
        this.nodes.set(key, this[head]);
       }
       else {
        if(this.nodes.has(key)) {
          this.update(key, val);
        } else {
            const node = this[head];
            this[head] = new DoublyLinkedListNode(val, key);
            this[head].next = node;
            node.previous = this[head];
            this.nodes.set(key, this[head]);
         }
       }
    }
    update(key, val) {
        const node = this.nodes.get(key);
        node.value = val;
        this.moveNodeToHead(node);
    }
    get(key){
        const node = this.nodes.get(key);
        if(node) {
            this.moveNodeToHead(node)
        }
        return node;
    }
    moveNodeToHead(node) {
        const prev = node.previos;
        const next = node.next;
        if(prev) prev.next = next;
        if(next) next.previous = prev;
        const h = this[head];
        this[head] = node;
        this[head].next = h.next;
    }
    removeTail() {
        const key = this[tail].index;
        const node = this.nodes.get(key);
        node.previous.next = null;
        this[tail] = node.previous;
        this.nodes.delete(key)
    }
    getLength() {
        return this.nodes.size;
    }
}

function LRUCache() {
    const hashTable = new DoublyLinkedListHashTable()
    const capacity = 5;
    return {
        get: function(key) {
            return hashTable.get(key)?.value;
        },
        set: function(key, value) {
           hashTable.add(key, value);
            if(hashTable.getLength() > capacity){
                hashTable.removeTail()
            }
        },
        print: function() {
           console.log(hashTable)
        }
    }
}