Javascript LinkedList head

Writing LinkedList data structure in Javascript:

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

    add(value) {
        const newNode = {
            value: value,
            next: null
        }

        if(!this.head) {
            this.head = newNode;
        }

        if(this.tail) {
            this.tail.next = newNode;
        }

        this.tail = newNode;

    }
}

const myLinedList = new LinkedList()
myLinedList.add('first value')
myLinedList.add('second values')
myLinedList.add('third values')

console.log(myLinedList)

… i don’t understand how head.next appears as no null. How the next for the head is written? I ask this because i add next only here this.tail.next but i don’t have any this.head.next.