[danShumway]

I might be misunderstanding what you're referring to. To be clear, I'm not really talking about recursively building anything about the HTML or fetching any additional data about other comments, or storing it in the database as a tree, a flat structure and iterative builds are fine for all of this. I'm talking about, purely off the top of my head, moving away from:

  result = reduce(comments, (result, comment) => {
    return result + build_comment(comment);
  }, '');

to:

  indent_level = 0;
  result = reduce(comments, (result, comment) => {
     missing_lvls = indent_level - comment.indent_level;
     close_str = missing_lvls > 0 ? repeat_str('</ul>', missing_lvls) : '';
     indent_level = comment.indent_level;

     return result + close_str + build_comment(comment);
  }, '');

I assume you're right and there's some kind of extra complexity somewhere, but HN isn't just storing the comments with no context other than indentation as far as I can tell. It is maintaining parent-child relationships at least well enough that the buttons to minimize/maximize threads work, so I am not sure what process is being skipped here by shipping flat HTML lists.

I guess I haven't ever read through HN's clientside Javascript, maybe it's calculating how to minimize threads on the fly completely clientside by iterating over the DOM, and maybe that's why the buttons don't work with JS disabled. But.. oof, I wouldn't hold that up as an example of good, simple clientside code if that's the case.

----

But again, I'm not going to argue with your conclusion, I assume there's something I've missed, I assume you're right.

This is still a bad example to use for "see, simple HTML is better". What you're describing is a good example of why it makes sense to say, "see, convoluted table setups that are worse on the client are faster overall than clean, simple output."

Which is not a bad lesson to learn from HN. It's a great lesson, sometimes performance requires us to do hacky things. But it is a very different lesson from where this thread started. You still would never point at that and say, "this is a good example of what HTML should look like", you would say, "these are the kinds of messy sacrifices that might be necessary to maintain a performant backend."

[danShumway]

> maybe it's calculating how to minimize threads on the fly completely clientside by iterating over the DOM, and maybe that's why the buttons don't work with JS disabled

Holy crud, I just opened the JS up and this is actually what it's doing. Heck me and my little 'not going to contradict you' statements, you might just be completely entirely right about what's going on I guess.

  function kidvis (tr, hide) {
    var n0 = ind(tr), n = ind(kid1(tr)), coll = false;
    if (n > n0) {
      while (tr = kid1(tr)) {
        if (ind(tr) <= n0) {

I'm still going to reassert that any architecture that leads to someone doing this kind of logic every time a button is pressed is neither simple nor elegant, and at best this is an example of making architectural sacrifices and introducing complexity for the sake of performance; there's no way that this kind of page logic is easier to maintain or to understand than something built around a more semantic structure.

It's also definitely not easier on the client, I've seen some comments on here argue that HN might use all this weird stuff to save client battery life, and I feel more confident now saying that's not the reason, because if someone is somehow, someway legitimately in some incredible situation where they're actually worried about the battery drain of a browser rendering a table vs a some extra CSS, then this is not the code you would want to run every single time you press a button on the page.

But yeah, the "we just base everything off of an indentation integer and comment order" theory does seem a lot more plausible to me now, because I'm having a somewhat difficult time thinking why else collapsing comments would work this way.