This is a sample problem using a Linked List.

The duplicate removal algorithm is implemented with an O(n) solution using a Map:

class LinkedList {
 ...

  removeDuplicates() {
    let previouslySeen  = new Map();

    let iterations      = this.count;
    let current         = this.head;
    let prev            = this.head;

    for (let i = 0; i < iterations; i++) {
      if (previouslySeen.has(current.value)) {
        if (current.next) {
          prev.next = current.next;
        } else {
          prev.next = null;
        }

        this.decrementCount();
      } else {
        previouslySeen.set(current.value, current);
        prev = current;
      }

      current = current.next;
    }
  }

 ...
}