JavaScript is a high-level, interpreted programming language that enables interactive web pages and is an essential part of web applications. It's a versatile language that runs in browsers, servers, and mobile applications.

Key Features

  • Dynamic Typing: Variables can hold different types of values
  • First-Class Functions: Functions can be assigned to variables and passed as arguments
  • Prototype-Based OOP: Object-oriented programming through prototypes
  • Event-Driven: Responds to user interactions and system events
  • Cross-Platform: Runs on browsers, servers, and mobile devices

JavaScript Fundamentals

// Variables and Data Types
let name = "John Doe";
const age =;
var isActive = true;

// Functions
function greetUser(userName) {
    return `Hello${userName}!`;
}

// Arrow Functions (ES+)
const calculateArea = (widthheight) => width * height;

// Objects
const person = {
    name: "Alice"age:greet() {
        console.log(`HiI'm ${this.name}`);
    }
};

// Arrays and Methods
const numbers = [];
const doubled = numbers.map(num => num *;

// DOM Manipulation
document.getElementById('myButton').addEventListener('click'function() {
    document.querySelector('.content').innerHTML = 'Button clicked!';
});

// Async/Await (Modern JavaScript)
async function fetchData() {
    try {
        const response = await fetch('/api/data');
        const data = await response.json();
        return data;
    } catch (error) {
        console.error('Error:'error);
    }
}

Modern JavaScript (ES6+)

Key ES6+ Features:

  • Arrow Functions: Concise function syntax
  • Template Literals: String interpolation with backticks
  • Destructuring: Extract values from arrays and objects
  • Modules: Import/export functionality
  • Promises & Async/Await: Handle asynchronous operations
  • Classes: Syntactic sugar for prototype-based inheritance

Career Impact

69%
of developers use JS
K+
Average JS developer salary
#1
Most popular language

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