Method append

chapter02/util/LinkedListX.js:29–40

(value)

    }
  
    append(value) {
        let node = new Node(value);
        // if list is empty
        if (!this.head) {
            this.head = node;
            this.tail = node;
        }
        else {
            this.tail.next = node;
            this.tail = node;
        }
    }
  
    prepend(value) {
        let node = new Node(value);