Nodejs Guide

Difference between Sync and Async File Methods

1. Definition

In Node.js, file operations can be performed using synchronous (sync) or asynchronous (async) methods. Sync methods block execution, while async methods allow other operations to run simultaneously.

2. Synchronous (Sync)

  • Blocking operation
  • Executes line by line
  • Stops program until task is completed
  • Simple but slower for large tasks

3. Asynchronous (Async)

  • Non-blocking operation
  • Does not stop execution
  • Uses callbacks, promises, or async/await
  • Faster and more efficient

4. Key Differences

  • Execution: Blocking vs Non-blocking
  • Performance: Slower vs Faster
  • Usage: Simple tasks vs Real-world apps
  • Handling: Direct return vs Callback/Promise

5. Example

👉 Synchronous

const fs = require("fs");

const data = fs.readFileSync("example.txt", "utf8");
console.log(data);
console.log("Done");

👉 Asynchronous

const fs = require("fs");

fs.readFile("example.txt", "utf8", (err, data) => {
  if (err) throw err;
  console.log(data);
});
console.log("Done");

6. Output Difference

// Sync Output
File Content
Done

// Async Output
Done
File Content

7. When to Use

  • Use Sync for small scripts or debugging
  • Use Async for real-world applications
  • Prefer Async for better performance