Node.js File System

The fs module reads and writes files. Prefer the promise version in modern code. This example uses a temporary folder.

ExampleNode.js

const fs = require("fs");
const os = require("os");
const path = require("path");

const dir = fs.mkdtempSync(path.join(os.tmpdir(), "wecode-"));
const file = path.join(dir, "notes.txt");

fs.writeFileSync(file, "line one\n");
fs.appendFileSync(file, "line two\n");
console.log(fs.readFileSync(file, "utf8"));
console.log(fs.existsSync(file));
console.log(fs.statSync(file).size, "bytes");
console.log(fs.readdirSync(dir));

fs.promises.readFile(file, "utf8").then((text) => {
  console.log(text.split("\n").length - 1, "lines");
  fs.rmSync(dir, { recursive: true });
  console.log(fs.existsSync(dir));
});

Output

line one
line two

true
18 bytes
[ 'notes.txt' ]
2 lines
false

Quick check

Which fs function reads a whole file at once (synchronously)?

readFileSyncopenFilegetFile

Finish the quick check (and any code exercise) to complete this lesson, or mark it done yourself.

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