Got it 👍 Let’s go through the basic knowledge of JavaScript step by step.

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🌐 What is JavaScript?

• JavaScript (JS) is a high-level, interpreted programming language mainly used to make web pages interactive and dynamic.
• It runs in the browser (client-side), but also on servers (using Node.js).
• Along with HTML (structure) and CSS (style), JavaScript is the third core technology of the web.

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✨ Key Features

• Lightweight & interpreted: No compilation needed, runs directly in the browser.
• Event-driven: Reacts to user actions like clicks, key presses, etc.
• Prototype-based OOP: Uses objects and prototypes instead of classical classes (though modern JS supports class).
• Cross-platform: Runs in all major browsers and environments (Node.js).

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📌 Basic Concepts

1. Variables

Used to store data.

let name = "Raj";   // Block-scoped, modern
var age = 20;       // Function-scoped, older
const PI = 3.14;    // Constant, cannot be reassigned

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2. Data Types

• Primitive: string, number, boolean, undefined, null, symbol, bigint
• Non-primitive: object, array, function

let str = "Hello";        // string
let num = 42;             // number
let isAlive = true;       // boolean
let x;                    // undefined
let y = null;             // null
let arr = [1, 2, 3];      // array
let obj = {name: "Raj"};  // object

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3. Operators

• Arithmetic: + - * / % **
• Assignment: = += -=
• Comparison: == === != !== > < >= <=
• Logical: && || !
• String: "Hello" + "World"

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4. Functions

Reusable blocks of code.

function greet(name) {
  return "Hello " + name;
}
console.log(greet("Raj"));

Arrow function (modern):

const add = (a, b) => a + b;
console.log(add(5, 3));

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5. Control Statements

let age = 18;
if (age >= 18) {
  console.log("Adult");
} else {
  console.log("Minor");
}

for (let i = 0; i < 5; i++) {
  console.log(i);
}

while (age < 21) {
  console.log("Growing...");
  age++;
}

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6. Objects & Arrays

// Object
let person = {
  name: "Raj",
  age: 20
};
console.log(person.name);

// Array
let fruits = ["Apple", "Banana", "Mango"];
console.log(fruits[1]);  // Banana

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7. Events & DOM

JavaScript can manipulate HTML & CSS via DOM (Document Object Model).

<button onclick="showMessage()">Click Me</button>

<script>
  function showMessage() {
    alert("Hello, Raj!");
  }
</script>

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8. ES6+ Features (Modern JS)

• Template literals: `Hello ${name}`
• Destructuring: let [a, b] = [10, 20]; let {name, age} = person;
• Promises & Async/Await for handling asynchronous code.
• Modules (import / export).