Stack implementation

Stack.ts

class Nodo {
    public next: Nodo = null;

    constructor(
        public value: number
    ) {}
}


class Stack {
    private head: Nodo = null;
    private length: number = 0;

    public push(value: number): void {
        const node = new Nodo(value);

        node.next = this.head; 
        this.head = node; // head = 2 -> 1 -> null
        this.length += 1;
    }

    public pop(): number {
        if (this.isEmpty()) {
            return null;
        }

        const value = this.head.value;
        this.head = this.head.next; // head = 1 -> null
        this.length -= 1;

        return value;
    }

    public peek(): number {
        if (this.isEmpty()) {
            return null;
        }

        return this.head.value;
    }

    public size(): number {
        return this.length;
    }

    public isEmpty(): boolean {
        return this.head == null;
    }
}


const s = new Stack();


console.log('IS EMPTY:', s.isEmpty());
s.push(1);
s.push(2);
s.push(3);
console.log('IS EMPTY:', s.isEmpty());
console.log('PEEK:', s.peek()); // 3
console.log('LEN:', s.size()); // 3


s.pop();
s.pop();
s.pop();
console.log('IS EMPTY:', s.isEmpty());
console.log('LEN:', s.size());