👉 Understanding readFileSync vs readFile vs fs.promises.readFile in Node.js 🚀

When working with file I/O operations in Node.js, choosing the right file reading method is crucial for optimizing performance and ensuring smooth execution of your application. Here's a quick breakdown of three common methods and when to use each:

1. readFileSync (Synchronous): Blocks the event loop until the file is completely read. Use it when you don’t need to execute further code while reading the file, and blocking is acceptable (e.g., startup tasks or simple scripts).

import { readFileSync } from "node:fs";

try {
  const data = fs.readFileSync("example.txt", "utf8");
  console.log("File contents:", data);
} catch (err) {
  console.error("Error reading file:", err);
}

2. readFile (Asynchronous with Callback): Non-blocking operation: allows other tasks to run while waiting for the file to be read. Use it when you need to handle other tasks concurrently while reading the file.

const fs = require('fs');

fs.writeFile('output.txt', 'Hello, World!', (err) => {
    if (err) {
        console.error('Error writing file:', err);
    } else {
        console.log('File written successfully!');
    }
});

3. fs.promises.readFile (Promise-based, with async/await): Similar to readFile, but allows you to work with Promises and async/await for cleaner, more readable code. Use it when you prefer Promises or async/await for error handling and cleaner syntax.

import { readFile } from 'node:fs/promises'

readFile('sample.txt', 'utf8')
    .then(data => console.log(data))
    .catch(err => console.error(err))

Summary:

• readFileSync: Use when:No further code execution is needed immediately. It's acceptable to block the event loop for the duration of the file read.
• readFile (callback-based) or fs.promises.readFile (Promise-based): Use when:You want to perform other tasks while the file is being read (non-blocking).You need better handling of asynchronous operations (especially with multiple tasks).

In short:

• readFileSync = Block until file is read (best for simple scripts or single operations with no concurrent I/O).
• readFile / fs.promises.readFile = Allow other code to run while waiting for the file (best for handling multiple tasks or concurrent I/O operations).

Let me know if you need more clarification!

💡 Tip: In modern Node.js apps, prefer fs.promises.readFile to take full advantage of async/await for better error handling and cleaner code! 🚀