Piye carane ngerjani sistem berkas ing Node?

Question

Accepted Answer

Module **`fs`** built-in maca lan nulis berkas lan direktori. Ngedohake telu API styles — **promises** (modern, pilihan utama), **callbacks** (async asli), lan **sync** (blocking) — supaya sampeyan bisa milih sing pas kanggo kahanane.

## The promise API (recommended)

```js
import { readFile, writeFile, mkdir, readdir } from "fs/promises";

async function work() {
  const data = await readFile("input.txt", "utf8");     // read (utf8 → string)
  await writeFile("output.txt", "Hello");                // write (overwrites)
  await mkdir("new-dir", { recursive: true });           // create dirs (recursive = mkdir -p)
  const files = await readdir("./");                      // list directory contents
}
```

API `fs/promises` kerjane rapi karo async/await — standar modern kanggo file I/O.

## Callback lan sync variants

```js
import fs from "fs";

fs.readFile("file.txt", "utf8", (err, data) => { ... }); // async callback
const data = fs.readFileSync("file.txt", "utf8");         // SYNC — blocks the event loop!
```

**Hati-hati:** Metode `*Sync` **ngalangi seluruh event loop** nganti operasi rampung. Bener-bener ing startup (loading config sekali) nanging kudu dihindari ing request handlers — reading sing ngalangi membekukan kabeh request concurrent.

## Operasi umum

```js
await fs.promises.appendFile("log.txt", "new line
"); // append
await fs.promises.unlink("old.txt");                    // delete a file
await fs.promises.rename("a.txt", "b.txt");             // rename/move
const stats = await fs.promises.stat("file.txt");       // metadata (size, mtime)
const exists = fs.existsSync("file.txt");               // check existence
```

## Kanggo berkas gedhe: gunakake streams

```js
// ❌ readFile loads the WHOLE file into memory — bad for huge files
const huge = await readFile("10gb.txt"); // could exhaust memory

// ✅ stream it in chunks (constant memory)
fs.createReadStream("10gb.txt").pipe(fs.createWriteStream("copy.txt"));
```

Kanggo berkas gedhe, `readFile` muati kabeh ing memory sapisan; **streams** ngolah data ing potongan karo memory konstan.

## Apa gunane

File I/O iku kaluarwargaan inti Node kanggo loading config, logging, file uploads/downloads, lan tooling.

Ngenalan telu API styles — lan penting, manawa **metode sync ngalangi event loop** (hindari ing servers) lan manawa **berkas gedhe butuh streams** (dudu `readFile`) — iku penting kanggo nulis kode file-handling sing bener lan efisien nang kalanuwakan.