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Anonymous Functions in JavaScript

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Anonymous functions are those functions that do not have any name. Just like an anonymous call or anonymous email has no identity, similarly, these functions also don’t have a defined name.


What is an Anonymous Function?

An anonymous function is a function without a name, and it is usually stored inside a variable.

Example:


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

Here:

  1. The function has no name
  2. It is assigned to a variable add


Calling the Function:


console.log(add(2, 2)); // Output: 4


Anonymous Function vs Function Expression

  1. Both are stored in variables
  2. The difference is:
  3. Function Expression can have a name
  4. Anonymous Function has no name


Where Do We Use Anonymous Functions?

Anonymous functions are mostly used as callback functions.

Example:


function operations(fun) {
let x = 10;
let y = 20;
console.log(fun(x, y));
}

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

const sub = function(a, b) {
return a - b;
}

operations(add); // 30
operations(sub); // -10

Here:

  1. operations is taking a function as a parameter
  2. add and sub are passed as arguments
  3. These act as callback functions


Another Example: setTimeout


const onTime = function() {
console.log("on time called");
}

setTimeout(onTime, 2000);

  1. setTimeout takes a function as a parameter
  2. That function is executed after a delay


Hoisting in Anonymous Functions

Anonymous functions behave like function expressions.

  1. You cannot call them before declaration

add(); // Error

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


Difference: Named Function vs Anonymous Function

  1. Named functions can be called inside themselves (useful in recursion)
  2. Anonymous functions cannot be called internally because they don’t have a name
  3. Debugging is easier with named functions
  4. Anonymous functions are commonly used in callbacks


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