JavaScript Learning Path

1// var (older way, function scoped)
2var name = "John";
3
4// let (block scoped, can be reassigned)
5let age = 25;
6age = 26; // This is valid
7
8// const (block scoped, cannot be reassigned)
9const PI = 3.14159;
10// PI = 3.14; // This would cause an error

1// Primitive types
2let string = "Hello";           // String
3let number = 42;                // Number
4let decimal = 3.14;             // Also a Number
5let boolean = true;             // Boolean
6let nullValue = null;           // Null
7let undefinedValue;             // Undefined
8let bigInt = 9007199254740991n; // BigInt
9let symbol = Symbol("unique");  // Symbol
10
11// Check the type using typeof
12console.log(typeof string);     // "string"
13console.log(typeof number);     // "number"
14console.log(typeof boolean);    // "boolean"
15
16// Complex type: Object
17let person = {
18  name: "Alice",
19  age: 30,
20  isStudent: false
21};
22
23// Arrays are also objects
24let fruits = ["apple", "banana", "orange"];
25
26console.log(typeof person);     // "object"
27console.log(typeof fruits);     // "object"
28console.log(Array.isArray(fruits)); // true

1let a = 10;
2let b = 3;
3
4console.log(a + b);  // Addition: 13
5console.log(a - b);  // Subtraction: 7
6console.log(a * b);  // Multiplication: 30
7console.log(a / b);  // Division: 3.3333...
8console.log(a % b);  // Modulus (remainder): 1
9console.log(a ** b); // Exponentiation: 1000 (10^3)
10
11// Increment and decrement
12let c = 5;
13console.log(c++);    // 5 (returns c, then increments)
14console.log(c);      // 6
15console.log(++c);    // 7 (increments c, then returns it)

1let x = 5;
2let y = "5";
3
4console.log(x == y);   // true (loose equality, converts types)
5console.log(x === y);  // false (strict equality, checks types)
6console.log(x != y);   // false (loose inequality)
7console.log(x !== y);  // true (strict inequality)
8console.log(x > 3);    // true
9console.log(x <= 5);   // true

1let isAdult = true;
2let hasLicense = false;
3
4console.log(isAdult && hasLicense); // AND: false
5console.log(isAdult || hasLicense); // OR: true
6console.log(!isAdult);              // NOT: false
7
8// Short-circuit evaluation
9let name = "";
10let defaultName = name || "Anonymous"; // "Anonymous"
11
12let user = { name: "John" };
13let userName = user && user.name;      // "John"

1let age = 18;
2
3// if statement
4if (age >= 18) {
5  console.log("You are an adult");
6}
7
8// if-else statement
9if (age >= 18) {
10  console.log("You are an adult");
11} else {
12  console.log("You are a minor");
13}
14
15// if-else if-else statement
16if (age < 13) {
17  console.log("Child");
18} else if (age < 18) {
19  console.log("Teenager");
20} else {
21  console.log("Adult");
22}
23
24// Ternary operator (condition ? trueValue : falseValue)
25let status = age >= 18 ? "Adult" : "Minor";
26console.log(status);
27
28// Switch statement
29let day = 2;
30switch (day) {
31  case 0:
32    console.log("Sunday");
33    break;
34  case 1:
35    console.log("Monday");
36    break;
37  case 2:
38    console.log("Tuesday");
39    break;
40  default:
41    console.log("Another day");
42}

1// for loop
2for (let i = 0; i < 5; i++) {
3  console.log("Iteration " + i);
4}
5
6// while loop
7let count = 0;
8while (count < 3) {
9  console.log("Count: " + count);
10  count++;
11}
12
13// do-while loop (always executes at least once)
14let num = 0;
15do {
16  console.log("Number: " + num);
17  num++;
18} while (num < 3);
19
20// for...of loop (iterates over iterable values)
21const colors = ["red", "green", "blue"];
22for (const color of colors) {
23  console.log(color);
24}
25
26// for...in loop (iterates over object properties)
27const person = { name: "John", age: 30, job: "developer" };
28for (const key in person) {
29  console.log(key + ": " + person[key]);
30}