All code using array.reduce should be rewritten without array.reduce so it's readable by humans https://twitter.com/jaffathecake/status/1213408744362692608 #gogofast

0-reduce.txt

Object transformations should not use reduce.

Creating an object once, then passing the same object back through reduce is using reduce for decoration only. The only part of reduce it's using is the looping.

The applicability of reduce() is pretty much limited to associative operators, and in all other cases it's better to write out the accumulation loop explicitly.

1-reduce.js

// Good
arr.reduce((total, item) => total + item);

// reduce used only as decoration
const obj = arr.reduce((obj, item) => {
  obj[item] = null;
  return obj;
}, {});

2-fromEntries.js

const obj = Object.fromEntries(
  arr.map(item => [item, null]),
);

3-loop.js

const obj = {};
for (const item of arr) obj[item] = null;