Why Bun Give Unsorted Output Files in Read Directory?

[kresnasatya]

Hi everyone! I create a script to get list of files inside of directory named books. Here's the directory structure:

- books
   - a.md
   - b.md
   - c.md
   - d.md
   - z.md

Here's the script.

// index.js
import path from 'node:path';
import fs from 'node:fs/promises';

(async () => {
    const files = await fs.readdir(path.join(process.cwd(), 'books'));
    for (const file of files) {
        console.log(file);
    }
})();

If I run node index.js I get the sorted output files (ascending).

// node index.js
a.md
b.md
c.md
d.md
z.md

Meanwhile, if I run bun index.js I get unsorted output files.

// bun index.js <= Run this command many times and I get the exact output below.

b.md
z.md
c.md
d.md
a.md

I'm using Bun version 1.1.26 on macOS M1. I'm curious why does it happened? Is that design by default or is it bug?

[Jarred-Sumner]

This is consistent with Node.js - the operating system determines what sorting order to use, which is essentially random

[kresnasatya]

Thanks for the answer, Jarred.

[alexeyten]

NodeJS (well, actually libuv) does sort files on Linux (Mac), but not on Windows.

See:
nodejs/node#3232
https://github.com/libuv/libuv/blob/v1.x/src/unix/fs.c#L580

I'm not saying that Bun should. I'm personally against implicit sorting.

[kresnasatya]

Thanks for detail information, alex.