`no-array-reduce`?

[fregante]

-> https://github.com/sindresorhus/eslint-plugin-unicorn/blob/v40.0.0/docs/rules/no-array-reduce.md

Does this package still make sense? Should it be deprecated?

p-reduce

import pReduce from 'p-reduce';
import humanInfo from 'human-info'; // Not a real module

const names = [
    getUser('sindresorhus').then(info => info.name),
    'Addy Osmani',
    'Pascal Hartig',
    'Stephen Sawchuk'
];

const totalAge = await pReduce(names, async (total, name) => {
    const info = await humanInfo(name);
    return total + info.age;
}, 0);

console.log(totalAge);
//=> 125

for of

import humanInfo from 'human-info'; // Not a real module

const names = [
    getUser('sindresorhus').then(info => info.name),
    'Addy Osmani',
    'Pascal Hartig',
    'Stephen Sawchuk'
];

let totalAge = 0;
for (const name of names) {
    const info = await humanInfo(name);
    totalAge += info.age;
}

console.log(totalAge);
//=> 125

[sindresorhus]

It's only somewhat useful in the rare case of summing up numbers, which is allowed by default.

• https://github.com/sindresorhus/eslint-plugin-unicorn/blob/v40.0.0/docs/rules/no-array-reduce.md

Which is what the example in the readme is doing.

[fregante]

I think not? There's a constant assignment and an await in there. It looks like a regular reduce loop to me, not the simple (t, b) => t+b exemption.

[sindresorhus]

The example shows summing up age, which is summing up a number, which is the only valid use-case for reduce.

[fregante]

Why is the only valid use-case? It's because "it does not require return" in practice, not just because it's a sum. I don't see a difference between:

const totalAge = await pReduce(names, async (total, name) => {
    const info = await humanInfo(name);
    return total + info.age;
}, 0);

and

const notTheTotal = await pReduce(names, async (total, name) => {
    const info = await humanInfo(name);
    return totallyNotSum(total, info.age);
}, {});

The amount of code and readability is equal IMO. The exception is only valid if the code were:

const notTheTotal = await pReduce(
    names,
    async (total, name) => total + await humanAge(name),
    0
);

and even then it's kind of a stretch because it's looping things in series when it could totally get humanAge in parallel. So not only is this package against no-array-reduce but also no-await-in-loop

Better yet:

// Parallel sum
const ages = await Promise.all(names.map(n => humanAge(n)));
const total = ages.reduce((t, a) => t + a)

or exclusively this, which isn't a huge improvement over the last example:

const ages = names.map(n => humanAge(n));
const total = await pReduce(ages, (t, a) => t + a)

[sindresorhus]

I'm talking about reduce in general, not what the lint rule is able to detect.

[fregante]

I'm not talking about the linter either, I'm just saying that the reasons for which no-array-reduce exists are the same for this package to not exist:

• reduce is unreadable other than for sums

additionally, the sum exception:

• should not apply to the readme example because it's a block function and has poor readability just like any other reduce PoCs
• is only applicable if you're reducing an Array<Promise<number>>, which saves just about 4 characters

furthermore:

• most examples go against no-await-in-loop too

[sindresorhus]

reduce is unreadable other than for sums

But the package literally recommends using it for sums.

should not apply to the readme example because it's a block function and has poor readability just like any other reduce PoCs

I disagree. The example is pretty clear.

is only applicable if you're reducing an Array<Promise>, which saves just about 4 characters

I do however agree that it's solving a very obscure problem and it's more likely to be abused for other things.

most examples go against no-await-in-loop too

Not sure what you mean? It's summing concurrently.

[sindresorhus]

In short. I disagree with some of your reasoning. But I agree with deprecating this package.

[sindresorhus]

https://github.com/sindresorhus/p-reduce/commit/c5777d0deebe0376138210ffae9011c8530d069d

[vladshcherbin]

It's quite amazing to read this message and then come across the p-waterfall source code, which is clearly not intended for performing number sum 😅

btw The note is not visible in npm readme since it was added after the latest release.