JavaScript's Reserved Keywords

let x = 0;

while (x < 10) {
  if (x === 5) {
    break;  // Exit the loop when x equals 5
  }
  console.log(x);
  x++;
}

// Output: 0, 1, 2, 3, 4

let fruit = "apple";

switch(fruit) {
  case "apple":
    console.log("It's an apple!");
    break;
  case "banana":
    console.log("It's a banana!");
    break;
  default:
    console.log("Unknown fruit.");
},// Output: It's an apple!

try {
  let data = JSON.parse('{"name": "John"');  // Invalid JSON
} catch (error) {
  console.log("Error parsing JSON: ", error.message);
},// Output: Error parsing JSON:  Unexpected end of input

class Person {
  constructor(name) {
    this.name = name;
  }

  greet() {
    console.log("Hello, " + this.name);
  }
}

const person1 = new Person("John");
person1.greet();  // Output: Hello, John

const pi = 3.14159;
console.log(pi);  // Output: 3.14159

// Reassigning pi will throw an error
// pi = 3.14;  // Uncaught TypeError: Assignment to constant variable.

for (let i = 0; i < 10; i++) {
  if (i % 2 === 0) {
    continue;  // Skip even numbers
  }
  console.log(i);  // Output: 1, 3, 5, 7, 9
}

function calculateSum(a, b) {
  let sum = a + b;
  debugger;  // Execution will pause here
  return sum;
}

calculateSum(5, 3);

let day = 3;

switch(day) {
  case 1:
    console.log("Monday");
    break;
  case 2:
    console.log("Tuesday");
    break;
  default:
    console.log("Unknown day");
    // Output: Unknown day
}

let person = { name: "John", age: 30 };

delete person.age;

console.log(person);  // Output: { name: "John" }

let i = 0;

do {
  console.log(i);
  i++;
} while (i < 5);
// Output: 0, 1, 2, 3, 4

let number = 10;

if (number > 20) {
  console.log("Number is greater than 20");
} else {
  console.log("Number is less than or equal to 20");  // Output: Number is less than or equal to 20
}

// module.js
export function greet(name) {
  return "Hello " + name;
}

// app.js
import { greet } from './module.js';
console.log(greet("Tom"));  // Output: Hello Tom

class Animal {
  constructor(name) {
    this.name = name;
  }

  speak() {
    console.log(this.name + " makes a sound");
  }
}

class Dog extends Animal {
  speak() {
    console.log(this.name + " barks");
  }
}

const dog = new Dog("Buddy");
dog.speak();  // Output: Buddy barks

try {
  let result = riskyOperation();
} catch (error) {
  console.log("Error occurred:", error);
} finally {
  console.log("This will always run.");
  // Output: This will always run.
}

for (let i = 0; i < 5; i++) {
  console.log(i);  // Output: 0, 1, 2, 3, 4
}

function add(a, b) {
  return a + b;
}

console.log(add(3, 4));  // Output: 7

let number = 10;

if (number > 0) {
  console.log("Number is positive");  // Output: Number is positive
}

// utils.js
export function greet(name) {
  return "Hello " + name;
}

// main.js
import { greet } from './utils.js';
console.log(greet("Tom"));  // Output: Hello Tom

const person = {
  name: "John",
  age: 30
};

console.log("name" in person);  // Output: true
console.log("address" in person);  // Output: false

class Animal {}
class Dog extends Animal {}

const dog = new Dog();
console.log(dog instanceof Dog);  // Output: true
console.log(dog instanceof Animal);  // Output: true
console.log(dog instanceof Object);  // Output: true

let x = 10;
if (true) {
  let x = 20; // Different variable than the one outside the block
  console.log(x); // Output: 20
}
console.log(x); // Output: 10

class Person {
  constructor(name) {
    this.name = name;
  }
}

const tom = new Person('Tom');
console.log(tom.name); // Output: Tom

function add(a, b) {
  return a + b;
}

const result = add(3, 4);
console.log(result); // Output: 7

class Animal {
  constructor(name) {
    this.name = name;
  }

  speak() {
    return `${this.name} makes a sound.`;
  }
}

class Dog extends Animal {
  constructor(name) {
    super(name);
  }

  speak() {
    return super.speak() + ' Woof!';
  }
}

const dog = new Dog('Buddy');
console.log(dog.speak()); // Output: Buddy makes a sound. Woof!

const color = 'blue';

switch (color) {
  case 'red':
    console.log('Red color');
    break;
  case 'blue':
    console.log('Blue color');
    break;
  default:
    console.log('Unknown color');
}

function divide(a, b) {
  if (b === 0) {
    throw new Error("Division by zero is not allowed.");
  }
  return a / b;
}

try {
  console.log(divide(4, 0));
} catch (e) {
  console.error(e.message); // Output: Division by zero is not allowed.
}

try {
  JSON.parse('invalid JSON');
} catch (error) {
  console.error("Parsing error:", error.message);
} finally {
  console.log("Attempted to parse JSON.");
}

console.log(typeof 42);         // Output: "number"
console.log(typeof 'hello');    // Output: "string"
console.log(typeof true);       // Output: "boolean"
console.log(typeof {});         // Output: "object"
console.log(typeof undefined);  // Output: "undefined"
console.log(typeof null);       // Output: "object" (quirk)

function example() {
  if (true) {
    var x = 10;
  }
  console.log(x); // Output: 10 (function scoped)
}

example();

console.log(void 0);         // Output: undefined
console.log(void (2 + 2));    // Output: undefined

// In HTML: <a href="javascript:void(0)">Click me</a>

let count = 0;
while (count < 3) {
  console.log('Count:', count);
  count++;
}
// Output:
// Count: 0
// Count: 1
// Count: 2

const obj = { a: 1, b: 2 };

with (obj) {
  console.log(a); // Output: 1
  console.log(b); // Output: 2
}

// Not allowed in strict mode

function* counter() {
  yield 1;
  yield 2;
  yield 3;
}

const gen = counter();
console.log(gen.next().value); // Output: 1
console.log(gen.next().value); // Output: 2
console.log(gen.next().value); // Output: 3