Simple linked list in JavaScript

Simple linked list in JavaScript.js

/* Linked List in EcmaScript */

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

}

class LinkedList {
    constructor (node) {
        this.root = node;
    }
    append (value) {
        let tmp = this.root;
        while(tmp.next) {
            tmp = tmp.next; // I wish there was tmp .= next;
        }
        tmp.next = new Node(value);
    }
    prepend (value) {
        let newNode = new Node(value);
        newNode.next = this.root;
        this.root = newNode;
    }
    print () {
        let tmp = this.root;
        while(tmp) {
            console.log(tmp.value);
            tmp = tmp.next;
        }
    }
    toString () {
        let tmp = this.root;
        let out = '';
        while(tmp) {
            out += ` ->  ${tmp.value}`;
            tmp = tmp.next;
        }
        out += ' -> null';
        return out;
    }
    sum () {
        let tmp = this.root;
        let out = 0;
        while(tmp) {
            out += tmp.value;
            tmp = tmp.next;
        }
        return out;
    }
}

class Run {
    static simpleCase () {
        let root = new Node(1);
        let list = new LinkedList(root);
        console.log(list.toString());
        list.append(2);
        console.log(list.toString());
        list.append(3);
        console.log(list.toString());
        list.append(4);
        console.log(list.toString());
        list.prepend(0);
        console.log(list.toString());
        list.print();
        console.log(list.toString());
        console.log(list.sum());
    }
}

Run.simpleCase();