Node.js File System | JavaScript Lesson

Lesson content

Read, practise, then check your understanding

node:fs/promises offers Promise operations; callback and synchronous variants serve different contexts. Use node:path for platform-aware paths and URLs for module-relative resources.

Bounded file work

import { readFile, writeFile } from "node:fs/promises";

const text = await readFile(filePath, "utf8");
await writeFile(outputPath, text.toUpperCase(), { flag: "wx" });

Encoding returns strings; omitted encoding returns Buffer bytes. Streams process large data incrementally and propagate backpressure. Validate resolved user paths against an allowed root, expect races between check/use, set permissions deliberately, and handle partial failure. Important replacements should write a temporary sibling then rename where platform semantics permit.

Knowledge check

Answer every question correctly to complete this chapter.

Which statement best describes node:fs/promises?

Which JavaScript term matches this description: Promise-based Node filesystem operations.

Which statement best describes Buffer?

Which JavaScript term matches this description: Node's byte container commonly used by binary I/O.

Which statement best describes stream?

Which JavaScript term matches this description: An abstraction processing data incrementally with backpressure.

Which statement best describes path module?

Which JavaScript term matches this description: Utilities for platform-correct filesystem path manipulation.

Which statement best describes atomic replacement?

Which JavaScript term matches this description: Writing a temporary file and renaming it over the destination.

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