JavaScript Anonymous Functions

• An anonymous function is a function without a name.
• It is often created using a function expression and is useful for short-term or situational usage.

Syntax (Function Expression):

const variableName = function(parameter1, parameter2, /* ... */) {
  // Code to be executed
};

• variableName: The variable that holds the anonymous function.
• parameter1, parameter2, ...: The parameters that the anonymous function accepts.

Why it is Used:

• Temporary Usage: Useful when a function is needed for a specific task and won't be reused elsewhere.
• Function as Argument: Frequently used as arguments to higher-order functions or event handlers.

Example:

// Anonymous Function as a Function Expression
const greet = function(name) {
  console.log('Hello, ' + name + '!');
};

// Calling the Anonymous Function
greet('John'); // Output: Hello, John!

Anonymous Function as Argument: Anonymous functions are commonly used as arguments to functions like setTimeout, map, filter, etc.

// Using Anonymous Function as an Argument
setTimeout(function() {
  console.log('This function will be executed after 2 seconds.');
}, 2000);

Immediately Invoked Function Expression (IIFE): An IIFE is an anonymous function that is immediately executed after being defined.

// IIFE Example
(function() {
  console.log('This is an IIFE.');
})();

ES6 Arrow Function: In ES6 and later versions, arrow functions provide a concise way to create anonymous functions.

// ES6 Arrow Function
const addNumbers = (a, b) => a + b;
console.log(addNumbers(3, 4)); // Output: 7

 

Summary

• Anonymous functions are functions without a name, often created using function expressions.
• They are useful for short-term tasks, as arguments to other functions, or for immediate execution using IIFE.
• Arrow functions in ES6 provide a concise syntax for creating anonymous functions.