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RomanKornev • today at 12:49 AM • 1 reply • view on HN

Every single `reduce` can be replaced with a more intuitive `groupBy`, `partition`, `mapValues`, `keyBy`, etc.

Reduce can approximate anything, that doesn't mean we should use it.

My favorite antipattern is

  items.reduce(
    (acc, item) => ({
      ...acc,
      [item.id]: item,
    }), {}
  );
Like, why? Not only is this ridiculously inefficient O(N^2), it's also longer and less understandable than "build a new map" version.

Replies

wingman-jr • today at 1:27 AM

I think this along with the other answers discussing the difficulty remembering the specific arguments of `reduce` (especially when varying by language!) are key reasons. After reading this conversational thread, I think maybe Microsoft got it right with LINQ: - `Where` is perhaps more intuitive than `filter` - `Select` seems no worse than `map` by invoking SQL-like syntax - While `reduce` is preserved as `Aggregate`, provide `GroupBy` and other handy methods as the preferred methods. In the code I write, it's probably these other methods that get called 95+% of the time. Who wants to `Aggregate` when they can simply `Sum` for example?