使用文件系统与流
学习如何在 Node.js 中使用 fs 模块同步或异步读写文件，并了解流如何帮助您高效处理大量数据。
使用文件系统与流 是 CoddyKit 上的免费 Node.js Backend Development Bootcamp 课时。 这是第 4 节课，共 4 节。 你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。 这是 Node.js Backend Development Bootcamp 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Node.js Backend Development Bootcamp 课程共包含 4 节课。
本课时的部分内容尚未翻译，以英文显示。
Why the File System Matters
Most backends eventually read or write files on disk — logs, config, uploads, reports. Node's built-in fs module handles it all; just require it.
const fs = require('fs');
console.log(typeof fs.readFile);Synchronous vs Asynchronous
Most fs methods come in two flavors: sync (like readFileSync) blocks the event loop, async doesn't. On servers, always prefer async.
const fs = require('fs');
const data = fs.readFileSync('config.txt', 'utf8');
console.log(data);Reading a File Asynchronously
The classic callback form gives you error first, then data. Always check err before touching the data — a missing file or bad permission lands there.
const fs = require('fs');
fs.readFile('notes.txt', 'utf8', (err, data) => {
if (err) { console.error('Failed:', err.message); return; }
console.log('File says:', data);
});The Promise-Based API
Modern Node exposes a promise-based API under fs/promises — pairs perfectly with async/await and skips callback nesting entirely.
const fs = require('fs/promises');
async function load() {
const data = await fs.readFile('notes.txt', 'utf8');
console.log(data);
}
load();Writing Files
Use writeFile to create or overwrite a file. No file? It's created. File exists? Its contents are replaced wholesale.
const fs = require('fs/promises');
async function save() {
await fs.writeFile('output.txt', 'Hello from Node!');
console.log('Saved.');
}
save();Appending Instead of Overwriting
To add to a file without wiping it, use appendFile — exactly what you want for log files that grow line by line.
const fs = require('fs/promises');
async function log(line) {
await fs.appendFile('app.log', line + '\n');
}
log('Server started');Working with Paths
Hard-coded paths break across operating systems. The path module fixes that: path.join uses the right separator, and __dirname is the current file's folder.
const path = require('path');
const full = path.join(__dirname, 'data', 'users.json');
console.log(full);Checking If a File Exists
Don't check existence first — that risks race conditions. Just try the operation and catch the error; a missing file throws with code ENOENT.
const fs = require('fs/promises');
async function read() {
try {
return await fs.readFile('maybe.txt', 'utf8');
} catch (err) {
if (err.code === 'ENOENT') return 'default content';
throw err;
}
}Why Streams Exist
Reading a 2 GB file with readFile loads it all into memory — a crash waiting to happen. Streams process data in small chunks, keeping memory low.
const fs = require('fs');
const stream = fs.createReadStream('huge.log', 'utf8');
stream.on('data', chunk => console.log('Got', chunk.length, 'bytes'));Piping Streams Together
The power move with streams is pipe: connect a readable straight to a writable. Node handles backpressure so a fast reader won't flood a slow writer.
const fs = require('fs');
const read = fs.createReadStream('input.txt');
const write = fs.createWriteStream('copy.txt');
read.pipe(write);Listing and Creating Directories
The fs module manages folders too: mkdir creates directories (add { recursive: true } for nested paths), and readdir lists contents.
const fs = require('fs/promises');
async function setup() {
await fs.mkdir('uploads', { recursive: true });
const files = await fs.readdir('.');
console.log(files);
}
setup();Quick Check
Test your understanding of file operations.
Recap
You can now work the file system: fs's sync/callback/promise APIs, async on servers, basic I/O, cross-platform path, and streams for big files.
常见问题解答
「使用文件系统与流」课时是免费的吗？
是的 — 「使用文件系统与流」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 Node.js Backend Development Bootcamp 课程的其余内容，请升级到 CoddyKit PRO。 Node.js Backend Development Bootcamp 课程共包含 4 节课。
「使用文件系统与流」这节课中我会学到什么？
学习如何在 Node.js 中使用 fs 模块同步或异步读写文件，并了解流如何帮助您高效处理大量数据。 你通过在浏览器中直接运行的动手代码来练习 Node.js Backend Development Bootcamp，全天候 AI 导师会在你学习这节课的过程中回答你的问题。
学习 Node.js Backend Development Bootcamp 需要有经验吗？
无需任何先前经验。CoddyKit 上的 Node.js Backend Development Bootcamp 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。 这是第 4 节课，共 4 节。
「使用文件系统与流」课时需要多长时间？
大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。
我能在这节 Node.js Backend Development Bootcamp 课中编写并运行代码吗？
能。每节 Node.js Backend Development Bootcamp 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。