JavaScript Callbacks

What are Callbacks?

Callbacks are functions passed as arguments to other functions. They execute later.

┌─────────────────────┐
│   Function A         │
│   ┌───────────────┐  │
│   │ callback()    │  │ ← Function passed in
│   └───────────────┘  │
└─────────────────────┘

Simple Example

function greet(name, callback) {
  console.log(`Hello, ${name}`);
  callback();
}

greet('John', () => {
  console.log('Callback executed!');
});

Common Use Cases

setTimeout(() => {
  console.log('Delayed');
}, 1000);

array.forEach(item => {
  console.log(item);
});

Key Takeaway

Callbacks are functions passed as arguments. Execute after main function completes. Used in timers, array methods, and async operations.