JavaScript Functions

noreply@example.com (AG Sayyed) — Mon, 24 Mar 2025 10:04:34 +0000

This document explains JavaScript functions, prototypes, and self-executing functions. It covers how functions are declared, how prototypes simplify the addition of properties and methods to objects, and how self-executing functions isolate variables and initialize data.

JavaScript Functions

Function Declaration and Usage

A function is a block of reusable code that can be called after being declared.
Functions consist of:
- The function keyword.
- A name for the function.
- Parentheses for optional parameters.
- Curly braces containing the logic.
- An optional return statement to return a value.

Example: Function Declaration

1function add(a, b) {
2 return a + b
3}
4console.log(add(5, 10)) // Output: 15

Functions in JavaScript are loosely typed, meaning the data type of arguments is determined at runtime.
Functions can return different types based on the input, such as adding numbers or concatenating strings.

JavaScript Prototypes

Overview of Prototypes

Prototypes allow properties and methods to be shared across all instances of an object.
Objects created with the new keyword inherit properties and methods from their prototype.

Example: Using Prototypes

 1function Car(make, model, year) {
 2 this.make = make
 3 this.model = model
 4 this.year = year
 5}
 6
 7Car.prototype.getName = function () {
 8 return `${this.make} ${this.model} (${this.year})`
 9}
10
11const car1 = new Car('Toyota', 'Corolla', 2020)
12console.log(car1.getName()) // Output: Toyota Corolla (2020)

Adding a method to a prototype ensures all instances of the object inherit the method.
Changes to the prototype are reflected in all instances.

Self-Executing Functions

What Are Self-Executing Functions

Self-executing functions, also known as auto-invocation or immediately invoked function expressions (IIFE), run immediately after being declared.
These functions isolate variables and logic from the global scope.

Example: Self-Executing Function

1;(function () {
2 const message = 'Hello, World!'
3 console.log(message)
4})() // Output: Hello, World!

Self-executing functions are often used for initialization tasks or to declare DOM elements.
Variables and functions inside an IIFE are not accessible outside of it.

Conclusion

JavaScript functions provide reusable blocks of code, while prototypes simplify the addition of shared properties and methods to objects. Self-executing functions isolate logic and variables, making them useful for initialization and encapsulation.

Javascript-Functions on Ghafoor's Personal Blog

JavaScript Functions