singly linked list implementation in js

singlyLinkedList.js

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

class SinglyLinkedList {
    constructor() {
        this.head = null;
        this.tail = null;
        this.length = 0;
    }

    // push: add node to end
    push(val) {
        var newNode = new Node(val)
        if (!this.head) {
            this.head = newNode
            this.tail = newNode
        } else {
            this.tail.next = newNode 
            this.tail = newNode
        }
        this.length++;
        return this;
    }

    // pop: remove node at end
    pop() {
        if (!this.head) return undefined;
        var current = this.head
        var newTail = current
        while (current.next) {
            newTail = current
            current = current.next;
        }
        this.tail = newTail;
        this.tail.next = null;
        this.length--;
        if (this.length === 0) {
            this.head = null;
            this.tail = null;
        }
        return current;
    }

    // shift: remove node from beginning
    shift() {
        if (!this.head) return undefined
        var oldHead = this.head;
        this.head = oldHead.next;
        this.length--
        if (this.length===0) {
            this.head = null;
            this.tail = null;
        }
        return oldHead
    }

    // unshift: add node to beginning
    unshift(val) {
        var newNode = new Node(val)
        if (!this.head) {
            this.head = newNode;
            this.tail = newNode;
        } else {
            newNode.next = this.head;
            this.head = newNode;
        }
        this.length++
        return this
    }

    // get: retrieve a node by its position
    get(idx) {
        if (idx < 0 || idx >= this.length) return null
        var counter = 0;
        var current = this.head
        while (counter !== idx) {
            current = current.next;
            counter++;
        }
        return current;
    }

    // set: change value of a node based on its position
    set(idx, val) {
        var foundNode = this.get(idx)
        if (foundNode) {
            foundNode.val = val
            return true;
        }
        return false;
    }

    // insert: insert node based on position
    insert(idx, val) {
        if (idx < 0 || idx > this.length) return false;
        if (idx === 0) { 
            this.unshift(val)
            return true;
        };
        if (idx === this.length) {
            this.push(val);
            return true;
        }; 
        var newNode = new Node(val);
        var beforeNode = this.get(idx-1);
        var afterNode = beforeNode.next;
        beforeNode.next = newNode;
        newNode.next = afterNode;
        this.length++;
        return true;
    }

    // remove: remove node based on position
    remove(idx) {
        if (idx < 0 || idx > this.length) return undefined;
        if (idx === this.length-1) {
            this.pop()
        }
        if (idx === 0) {
            this.shift()
        }
        var prevNode = this.get(idx-1)
        var removeNode = prevNode.next
        prevNode.next = removeNode.next
        this.length--;
        return removeNode;
    }
  
}