/**
* Definition for singly-linked list.
* function ListNode(val, next) {
* this.val = (val===undefined ? 0 : val)
* this.next = (next===undefined ? null : next)
* }
*/
/**
* @param {ListNode} head
* @return {ListNode}
*/
var deleteDuplicates = function (head) {
let current = head;
while (current !== null && current.next !== null) {
if (current.val === current.next.val) {
current.next = current.next.next;
} else {
current = current.next;
}
}
return head;
};