Stack Implementation in Javascript

stack-javascript.js

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

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

    push(val){
        let newNode = new Node(val)
        if (this.length === 0){
            this.first = newNode;
            this.last = newNode;
            
        }else{
           let temp = this.first;
           this.first = newNode;
           this.first.next= temp;
        }
        this.length++;     
        return this.length;
    }

    pop(){
        if (this.length === 0) return null;

        let temp = this.first;

        if (this.length === 1){
            this.last = null;
        }        
        this.first = this.first.next;        
        this.length--;
        return temp;
    }

}

Thank you for that.

For anyone looking to use this implementation in a project alongside Bootstrap, please change the name of Node class. Otherwise Bootstrap components will not work properly because Bootstrap has a Node class too.