Day-28 Understanding Anonymous Functions in JavaScript

JavaScript is full of powerful and flexible ways to write code. One such feature is the anonymous function — a function without a name. Today, I learned how they work, and I’m excited to share it!

What is an Anonymous Function?

An anonymous function is a function that’s not bound to an identifier (name). It’s usually used as a value — for example, passed as an argument or assigned to a variable.

Syntax:

function () {
  console.log("I'm anonymous!");
}

This function alone will throw an error — because in JavaScript, functions need to be declared or used immediately. So anonymous functions are often used like this:

Example 1: Assigned to a Variable

const greet = function() {
  console.log("Hello from an anonymous function!");
};
greet(); // Output: Hello from an anonymous function!

Example 2: Passed as a Callback

setTimeout(function() {
  console.log("Executed after 1 second");
}, 1000);

Why Use Anonymous Functions?

• Cleaner code for short, one-time-use functions
• Callbacks in asynchronous code
• Functional programming (like map(), filter(), etc.)

Anonymous Functions vs Arrow Functions

Arrow functions are often anonymous too! Here’s a comparison:

// Anonymous function
const add = function(a, b) {
  return a + b;
};

// Arrow function (also anonymous)
const addArrow = (a, b) => a + b;

Arrow functions are shorter and don't bind this, which makes them useful in many situations.

When Should You Use Them?

Use anonymous functions when:

• The function is small and simple
• It's used only once
• You’re writing inline callbacks

Avoid them when:

• You need to reuse the function
• You want to debug (named functions show up better in stack traces)

Summary

• Anonymous functions are functions without names.
• They're commonly used in callbacks, event handlers, and functional methods.
• Use them to keep your code concise and readable — but don’t overdo it!

Pro Tip: If you find yourself using the same anonymous function multiple times, consider naming it!