Introduction#
JavaScript is one of the most popular programming languages in the world. Whether you're building websites, mobile apps, or server-side applications, JavaScript is everywhere.
In this tutorial, we'll explore the fundamentals of JavaScript and how to get started.
Variables and Data Types#
JavaScript has several ways to declare variables:
// Modern way (ES6+)
let name = "Alice"; // Can be reassigned
const PI = 3.14159; // Cannot be reassigned
var oldStyle = "legacy"; // Avoid using var
// Data types
let string = "Hello, World!";
let number = 42;
let boolean = true;
let nothing = null;
let notDefined = undefined;
let obj = { key: "value" };
let arr = [1, 2, 3];
Functions#
Functions are first-class citizens in JavaScript:
// Function declaration
function greet(name) {
return `Hello, ${name}!`;
}
// Arrow function (ES6+)
const greet = (name) => `Hello, ${name}!`;
// Async function
async function fetchData(url) {
const response = await fetch(url);
const data = await response.json();
return data;
}
Arrays and Objects#
Working with data structures in JavaScript:
// Array methods
const numbers = [1, 2, 3, 4, 5];
const doubled = numbers.map(n => n * 2);
const evens = numbers.filter(n => n % 2 === 0);
const sum = numbers.reduce((acc, n) => acc + n, 0);
// Object destructuring
const { name, age, ...rest } = user;
// Spread operator
const newArray = [...arr1, ...arr2];
const newObj = { ...obj1, ...obj2 };
Promises and Async/Await#
Modern JavaScript handles asynchronous code elegantly:
// Promise chain
fetch('/api/data')
.then(res => res.json())
.then(data => console.log(data))
.catch(err => console.error(err));
// Async/Await (cleaner syntax)
async function getData() {
try {
const res = await fetch('/api/data');
const data = await res.json();
console.log(data);
} catch (err) {
console.error(err);
}
}
Conclusion#
JavaScript is a powerful and versatile language. By mastering its fundamentals, you'll be ready to build modern web applications and dive deeper into frameworks like React, Vue, or Node.js.
Pro Tip: Practice daily coding challenges on platforms like LeetCode to reinforce your JavaScript skills!
