myStack_LL.js

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

class Stack {
    constructor() {
        this.top = null;
        this.bottom = null;
        this.length = 0;
    }

    // Print the items in the stack.
    printList() {
        let list = [];
        let currentNode = this.top;
        while(currentNode !== null) {
            list.push(currentNode.value);
            currentNode = currentNode.next;
        }
        console.log(list.join(' --> '));
        return this.length;
    }

    // Return the top element.
    peek() {
        this.length ? console.log(this.top.value) : console.log('The stack is empty.');
				return this.length
    }

    // Insert the element at the top of the stack.
    push(value) {
        const newNode = new Node(value);

        if (this.length === 0) {
            this.top = newNode;
            this.bottom = newNode;
        } else {
            newNode.next = this.top;
            this.top = newNode;
        }

        this.length++;
        return this.printList();
    }

    // Pop the top element
    pop() {
        if (!this.length) {
            this.bottom = null;    // Remove the reference in this.bottom  
            console.log('The stack is empty.');
            return;
        }

        const tempNode = this.top;
        this.top = tempNode.next;
        
        this.length--;
        
        console.log(tempNode.value);
        return tempNode.value;
    }
}

const myStack = new Stack();

myStack.push('Udemy');                  // Udemy
myStack.push('Google');                 // Google --> Udemy
myStack.push('Discord');                // Discord --> Google --> Udemy

myStack.peek();                         // Discord

myStack.pop();                          // Discord
myStack.pop();                          // Google
myStack.pop();                          // Udemy
myStack.pop();                          // The stack is empty.