JavaScript Anonymous Functions

An anonymous function is a function without a name, mainly used for specific or short-term tasks, and is often assigned to variables or passed as arguments where reuse is not required.

• It omits the function name and is defined using the function keyword or arrow syntax.
• It is commonly used as callbacks or for one-time execution within a limited scope.

Syntax:

The below-enlightened syntax illustrates the declaration of an anonymous function using the normal declaration:

function () {
 // Function Body
}

We may also declare an anonymous function using the arrow function technique which is shown below:

() => {
 // Function Body...
}

Note: Parentheses are only required when immediately invoking an anonymous arrow function (IIFE). They are not required for defining a standalone anonymous arrow function.

[Example 1]: An anonymous function is defined to print a message, stored in the greet variable, and executed by calling greet().

[Example 2] : Passing arguments to the anonymous function.

As JavaScript supports Higher-Order Functions, we can also pass anonymous functions as parameters into another function.

[Example 3]: Passing an anonymous function as a callback function to the setTimeout() method. This executes this anonymous function 2000ms later.

Self-Executing Anonymous Functions

Another common use of anonymous functions is to create self-executing functions (also known as IIFE - Immediately Invoked Function Expressions). These functions run immediately after they are defined.

[Example]: Creating a self-executing function.

Arrow functions

Arrow Functions are a shorter ES6 syntax for writing anonymous functions, where the function keyword is not required and => is used to define the function.

• They provide a more concise and readable syntax.
• Commonly used for callbacks and short function expressions.

[Example 1] : This is an example of anonymous function with arrow function.

• If an arrow function has only one statement, curly braces {} can be omitted.
• The result of that statement is returned automatically without using return.

[Example 2]: A simple arrow function with a single expression is used.

[Example 3]: lllustrates a self-executing function (IIFE), which immediately invokes itself after being defined