It is too easy to write O(n^2) code using reduce, in fact I wrote an eslint rule to catch a common pattern I see other developers write.

- https://github.com/romellem/eslint-plugin-no-spread-in-reduc...

It catches code that looks like this:

    items.reduce((acc, item) => {
      return {
        ...acc,
        [item.id]: item
      };
    });