var reverseList = function(head) {
let prev = null;
let curr = head;
let nextTemp = null;
while(curr!= null) {
nextTemp = curr.next; // As I explained earlier, I save the next pointer in the temp variable.
curr.next = prev; // Then I reverse the pointer of the current node to its previous node.
prev = curr; // The previous node becomes the node we are currently at.
curr = nextTemp; // And the current nodes becomes the
next node we saved earlier. And we keep iterating.
}
return prev // At the end, our previous node will be the head node of the new list.
};