JavaScript Fundamentals

JavaScript is the programming language of the web. This guide covers the essential concepts you need to know.

Variables and Data Types

// Variables
let name = "John";
const age = 25;
var isStudent = true;

// Data types
let number = 42;
let string = "Hello World";
let boolean = true;
let array = [1, 2, 3];
let object = { name: "John", age: 25 };

Functions

// Function declaration
function greet(name) {
    return `Hello, ${name}!`;
}

// Arrow function
const add = (a, b) => a + b;

// Function expression
const multiply = function(a, b) {
    return a * b;
};

Control Flow

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

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

// While loop
let count = 0;
while (count < 3) {
    console.log(count);
    count++;
}

Objects and Arrays

// Object
const person = {
    name: "Alice",
    age: 30,
    greet() {
        return `Hi, I'm ${this.name}`;
    }
};

// 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);

Master these fundamentals and you'll have a solid foundation for JavaScript development!