Remove duplicates from a linked list

removeDuplicates.ts

function deleteDuplicates(head: Node): Node {
  const occurredVals = new Map()
  let node = head
  occurredVals.set(node.data, true)
  while (node.next != null) {
    if (occurredVals.get(node.next.data) === true) {
      node.next = node.next.next 
    } else {
      occurredVals.set(node.next.data, true)
      node = node.next
    }
  }

  return head
}

class Node {
  next:any 
  data: number

  constructor(num: number) {
    this.data = num
  }

  appendToTail = (num: number) => {
    const newNode = new Node(num)
    let node = this
    while (node.next != null) {
      node = node.next
    }
    node.next = newNode
  }
}

/*
    const node1 = new Node(1)
    node1.appendToTail(2)
    node1.appendToTail(1)
    node1.appendToTail(1)
    node1.appendToTail(3)
    node1.appendToTail(3)

    console.log(deleteDuplicates(node1))
*/