Apa iku stream ing Node.js lan kapan padha kudu digunakake?

Question

IT Interview Practice · Accepted Answer

**Stream** ngolah data **kanthi inkremental, ing potongan**, tinimbang ngloding kabeh ing memori bebarengan. Iki ndadekake penting kanggo data gedhe (file gedhe, transfer jaringan) nalika nglundhugi kabeh bakal ngabisin memori.

## Masalah sing dipisahake stream

```js
// ❌ loads the ENTIRE file into memory — crashes on a 10GB file
const data = await fs.promises.readFile("huge.csv");
process(data);

// ✅ stream it — constant memory, processes chunk by chunk
fs.createReadStream("huge.csv")
  .pipe(transform)
  .pipe(fs.createWriteStream("out.csv"));
```

Karo stream, penggunaan memori tetep rata koyo-koyo ukuran file — sampeyan nangani siji potongan ing wektu.

## Papat jinis stream

```text
Readable  → source you read FROM (fs.createReadStream, http request)
Writable  → destination you write TO (fs.createWriteStream, http response)
Duplex    → both readable & writable (TCP socket)
Transform → modify data as it passes through (zlib gzip, encryption)
```

## pipe — sambung stream

```js
import { createReadStream, createWriteStream } from "fs";
import { createGzip } from "zlib";

// read → compress → write, all streaming, low memory
createReadStream("file.txt")
  .pipe(createGzip())            // Transform: compress on the fly
  .pipe(createWriteStream("file.txt.gz"));
```

`pipe` nyambung readable menyang writable (karo transformasi ing tengah), otomatis nangani aliran — cara idiomatik kanggo nggabung stream.

## pipeline — pipe karo pananganan error sing tepat

```js
import { pipeline } from "stream/promises";

await pipeline(
  createReadStream("in.txt"),
  createGzip(),
  createWriteStream("out.gz")
); // ✅ cleans up all streams on error/completion (pipe alone leaks on errors)
```

`pipeline` luwih disenengi tinimbang `.pipe()` sing disambung amarga nenyebarake error lan nbersihin saben stream kanthi bener.

## Jinis stream nang ngrumayu

```text
✓ HTTP request/response bodies (req and res ARE streams)
✓ File reading/writing, file uploads/downloads
✓ Compression (zlib), encryption (crypto)
✓ Database cursors, large query results
✓ Real-time data processing, video streaming
```

## Nalika DUDU kuwatir

```text
Small data that fits comfortably in memory → readFile/simple buffering is simpler.
Streams add complexity; use them for LARGE or continuous data.
```

## Dene iki penting

Stream minangka fitur penentu Node kanggo pananganan data gedhe utawa terus-terusan sing **efisien memori** — beda antarane app sing kacilakan nalika unggah gedhe lan sing nangani ukuran apa wae kanthi memori rata.

Pamahaman papat jinis, komposisi `pipe`/`pipeline` (lan dene `pipeline` luwih aman), lan yen HTTP request/response dhewe-dhewe stream, penting kanggo nggawe layanan penanganan file, pemrosesan data, lan proxy sing bisa diskalake ing Node.

Masalah sing dipisahake stream

Papat jinis stream

pipe — sambung stream

pipeline — pipe karo pananganan error sing tepat

Jinis stream nang ngrumayu

Nalika DUDU kuwatir

Dene iki penting

Pitakon sing gegandhengan