Linked List basics

Code using JS

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

class LinkedList {
    constructor() {
        this.head = null;
    }

    addFirst(data) {
        const newNode = new Node(data);
        newNode.next = this.head;
        this.head = newNode;
    }
 
    addLast(data){
        const newNode = new Node(data);
        if(!this.head) {
            this.head = newNode()
            return
        }

        let current = this.head;
        while(current.next){
            current = current.next
        }

        current.next = newNode;
    }

    size(){
        let count = 0;
        let current = this.head
        while(current){
            count++;
            current = current.next;
        }
        return count;
    }

    addAt(index, data) {
        if(index < 0 || index > this.size()) {
            console.log("Invalid Index");
            return;
        }

        const newNode = new Node(data);
        if(index === 0){
            newNode.next = this.head;
            this.head = newNode;
            return;
        }

        let current = this.head;
        for(let i=0; i < index-1; i++) {
            current = current.next
        }

        newNode.next = current.next;
        current.next = newNode;
    }

    removeTop() {
        if(!this.head) {
            return
        }

        this.head = this.head.next;
    }

    removeLast() {
        if(!this.head){
            return;
        }

        let current = this.head;
        while(current.next.next) {
            current = current.next;
        }
        current.next = null;;

    }

    removeAt(index) {
        if(index < 0 || index > this.size()) {
            console.log("Invalid Index");
            return;     
        }

        if(index === 0) {
            this.head = newNode;
            return;
        }

        let current = this.head;
        for(let i = 9; i< index - 1; i++) {
            current = current.next;
        }

        if(current.next){ß
            current.next = current.next.next;
        }

        
    }
    print() {
        let current = this.head;
        while(current) {
            console.log(current.data);
            current = current.next;
        }
    }

}

const linkedList = new LinkedList()

linkedList.addFirst(5);
linkedList.addFirst(9);
linkedList.addFirst(3);
linkedList.addLast(111);
linkedList.addAt(3, 222);



linkedList.print();
console.log('=============')
linkedList.removeTop()
linkedList.print();

console.log(

    linkedList.size()
)