JavaScript

Java Script function show() { let a=20; var b=30; console.log(a); console.log(b); } show(); console.log(a); console.log(b);

https://github.com/sonyphoebeb/JavaScript-/blob/main/README.mdHere’s a crisp breakdown of JavaScript methods—categorized for clarity and speed 🔥

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🧠 Core Object Methods

These are built into JavaScript objects:

Object Type	Common Methods
Array	push(), pop(), shift(), unshift(), slice(), splice(), map(), filter(), reduce(), forEach()
String	charAt(), includes(), indexOf(), slice(), substring(), toUpperCase(), toLowerCase(), trim()
Object	hasOwnProperty(), keys(), values(), entries(), assign()
Number	toFixed(), toString(), parseInt(), parseFloat()
Date	getDate(), getMonth(), getFullYear(), setDate(), toISOString()

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⚙️ Functional Methods

Used for logic and control:

• setTimeout(), setInterval()
• clearTimeout(), clearInterval()
• typeof, instanceof

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🌐 DOM Methods (Browser-side)

Used to interact with HTML:

• document.getElementById()
• document.querySelector()
• element.addEventListener()
• element.classList.add(), remove(), toggle()
• element.setAttribute(), getAttribute()

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🧪 Utility Methods

Handy for debugging and data handling:

• JSON.stringify(), JSON.parse()
• console.log(), console.error(), console.table()

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Object-Oriented Programming (OOP) in JavaScript

JavaScript supports OOP (Object-Oriented Programming) using prototypes and ES6 class syntax.
OOP is based on 4 main principles: Encapsulation, Abstraction, Inheritance, and Polymorphism.

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🔹 1. Encapsulation (Data Hiding)

Encapsulation means bundling data (properties) and methods (functions) together in one unit (class/object).

class Person {
  #ssn; // private property
  constructor(name, ssn) {
    this.name = name;
    this.#ssn = ssn;
  }
  getDetails() {
    return `Name: ${this.name}, SSN: [HIDDEN]`;
  }
}

const p1 = new Person("Alice", "123-45-6789");
console.log(p1.getDetails()); 
// Output: Name: Alice, SSN: [HIDDEN]

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🔹 2. Abstraction (Hiding Implementation)

Abstraction hides unnecessary implementation details and exposes only the required functionality.

class Vehicle {
  start() {
    console.log("Starting the vehicle...");
  }
}

class Car extends Vehicle {
  start() {
    console.log("Car engine started ✅");
  }
}

const car = new Car();
car.start(); 
// Output: Car engine started ✅

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🔹 3. Inheritance (Code Reuse)

Inheritance allows one class to reuse properties and methods from another class.

class Animal {
  constructor(name) {
    this.name = name;
  }
  speak() {
    console.log(`${this.name} makes a sound.`);
  }
}

class Dog extends Animal {
  speak() {
    console.log(`${this.name} barks.`);
  }
}

const d = new Dog("Tommy");
d.speak(); 
// Output: Tommy barks.

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🔹 4. Polymorphism (Many Forms)

Polymorphism allows the same method to behave differently depending on the object.

class Shape {
  area() {
    return 0;
  }
}

class Circle extends Shape {
  constructor(radius) {
    super();
    this.radius = radius;
  }
  area() {
    return Math.PI * this.radius * this.radius;
  }
}

const c = new Circle(5);
console.log(c.area()); 
// Output: 78.54

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🔹 Other OOP Features in JavaScript

• Objects → The building blocks of OOP.
• Constructors → Special functions to initialize objects.
• Prototypes → Mechanism for inheritance.
• this keyword → Refers to the current instance.

function Person(name) {
  this.name = name;
}
Person.prototype.sayHello = function () {
  console.log(`Hello, my name is ${this.name}`);
};

const p = new Person("Alice");
p.sayHello(); 
// Output: Hello, my name is Alice

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✅ Summary

• Encapsulation → Bundle + hide data.
• Abstraction → Hide complexity.
• Inheritance → Reuse code.
• Polymorphism → Different behavior, same method.

JavaScript supports OOP through prototypes and ES6 classes.

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