Stack

stack.js

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

class Stack {
    constructor() {
        this.first = null;
        this.last = null;
        this.size = 0;
    }

    push(value) {
        const newNode = new Node(value);

        if (!this.first) {
            this.first = newNode;
            this.last = newNode;
        } else {
            const temp = this.first;
            this.first = newNode;
            this.first.next = temp;
        }

        return ++this.size;
    }

    pop() {
        if (!this.first) return null;

        const popped = this.first;

        if (this.first === this.last) {
            this.last = null;
        } 
        
        this.first = popped.next;

        this.size--;

        return popped.value;
    }
}

const stack = new Stack();
// stack.push(12);
// stack.push(1);
stack.push(120);

stack.pop();