CODEWITHSUNDEEP
javascriptlinked-list
StockDC2
StockDC2

Reputation: 163

Linked List - Removing Last Node

I am creating a function to remove the last node of a given list (inputted as an argument). The function itself is quite simple as shown below.

function popBack(list) {
    var current = list.head,
        previous;

    while (current.next) {
        previous = current;
        current = current.next;
    }

    // console.log(current);
    // console.log(previous.next);
    // current = null;
    // console.log(current);
    // console.log(previous.next);

    previous.next = null;
    return list;
}

Since the next node in the list is referenced by the one before it, previous.next and current should point to the same object. This brings me to my question. If I set current equal to null, wouldn't that make previous.next equal to null as well? This doesn't seem to be the case, as previous.next still references what current used to be. Can anyone please explain why this is happening?

Thanks in advance.

Upvotes: 0

Views: 1195

Answers (1)

Peter Olson
Peter Olson

Reputation: 142977

You are right that previous.next and current point to the same object. Let's call that object O. That is,

  • previous.next points to O.
  • current points to O.

When you run the following code,

current = null;

it doesn't set O to null, it only changes what current points to. That is, after current = null; is run, this is the new state:

  • previous.next points to O.
  • current points to null.

Upvotes: 2

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