? JavaScript Callbacks

What is a Callback?

• A callback is a function passed as an argument to another function.

• It is called (invoked) after some operation finishes, especially asynchronous ones.

• Enables code to run after an event or async task completes.

Basic Example of Callback

function greet(name, callback) {  console.log(`Hello, ${name}!`);  callback();}function sayGoodbye() {  console.log("Goodbye!");}greet("Alice", sayGoodbye);// Output:// Hello, Alice!// Goodbye!

Callbacks with Asynchronous Code

function fetchData(callback) {  setTimeout(() => {    callback("Data loaded");  }, 1000);}fetchData((message) => {  console.log(message);});

• The callback runs after 1 second, simulating an async operation.

Why Use Callbacks?

• Handle async operations like:

  • Fetching data

  • Timers

  • Event handling

• Maintain order of execution for async tasks.

Callback Hell (Pyramid of Doom)

• Nesting many callbacks leads to hard-to-read code:

doSomething(function(result) {  doSomethingElse(result, function(newResult) {    doThirdThing(newResult, function(finalResult) {      console.log("Done!");    });  });});

Alternatives to Callbacks

• Promises and Async/Await are modern, cleaner ways to handle async flows.

Want me to show you how to convert callback code into Promises or explain callback error handling?