<s>[INST] Here is a code snippet for a singly linked list in JavaScript:
```
class Node {
  constructor(data = null) {
    this.data = data;
    this.next = null;
  }
}

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

  append(data) {
    if (!this.head) {
      this.head = new Node(data);
    } else {
      let current = this.head;
      while (current.next) {
        current = current.next;
      }
      current.next = new Node(data);
    }
  }

  printList() {
    let current = this.head;
    while (current) {
      console.log(current.data);
      current = current.next;
    }
  }
}
```
How can I improve this code? 

I would like to know if there's any good practice I could incorporate in this code, and also if there are any potential errors that I have not accounted for.[/INST]