Javascript Program For Removing All Occurrences Of Duplicates From A Sorted Linked List

// Javascript program to remove all 
// occurrences of duplicates from a 
// sorted linked list 

// Class to create Linked lIst 
// head of linked list
let head = null;

class Node{

constructor(val) 
{
    // Default value of the next 
    // pointer field
    this.val = val;
    this.next = null;
}
}

// Function to insert data nodes into
// the Linked List at the front
function insert(data) 
{
    let new_node = new Node(data);
    new_node.next = head;
    head = new_node;
}

// Function to remove all occurrences
// of duplicate elements
function removeAllDuplicates() 
{
    // Create a dummy node that acts like 
    // a fake head of list pointing to the 
    // original head
    let dummy = new Node(0);

    // Dummy node points to the original head
    dummy.next = head;
    
    let prev = dummy;
    let current = head;

    while (current != null) 
    {
        // Until the current and previous values
        // are same, keep updating current
        while (current.next != null && 
               prev.next.val == current.next.val)
            current = current.next;

        // If current has unique value i.e current
        // is not updated, Move the prev pointer
        // to next node
        if (prev.next == current)
            prev = prev.next;

        // When current is updated to the last
        // duplicate value of that segment, make
        // prev the next of current
        else
            prev.next = current.next;

        current = current.next;
    }

    // Update original head to the next of 
    // dummy node
    head = dummy.next;
}

// Function to print the list elements
function printList() 
{
    let trav = head;
    if (head == null)
        console.log(" List is empty");

    while (trav != null) 
    {
        console.log(trav.val + " ");
        trav = trav.next;
    }
}

// Driver code
insert(53);
insert(53);
insert(49);
insert(49);
insert(35);
insert(28);
insert(28);
insert(23);

console.log("Before removal of duplicates:");
printList();

removeAllDuplicates();

console.log("After removal of duplicates:");
printList();
// This code is contributed by umadevi9616