Define the following variables using the appropriate keywords (let, const):

1. A variable named `userName` with the value "Ahmed" (mutable).
2. A variable named `PI` with the value 3.14 (immutable).
3. Try changing `PI` to 3.15 and explain what happens in a comment.

let userName = "Ahmed";
const PI = 3.14;

// PI = 3.15;
// This will throw a TypeError because const variables cannot be reassigned.

Create variables that represent the following types:

1. A string named `message` containing "Hello".
2. A number named `age` with the value 25.
3. A boolean named `isStudent` with the value true.
4. Check the type of `age` using `typeof` and log the result to the console.

let message = "Hello";
let age = 25;
let isStudent = true;

console.log(typeof age); // "number"

Perform the following operations:

1. Define two variables `x = 10` and `y = 5`.
2. Print their sum.
3. Print their product.
4. Print the remainder of `x` divided by `3` (modulus).

let x = 10;
let y = 5;

console.log(x + y); // 15
console.log(x * y); // 50
console.log(x % 3); // 1 (10 / 3 = 3 remainder 1)

Build a full sentence:

1. You have the variables: `firstName = "Ali"`, `lastName = "Mohammed"`.
2. Create a `fullName` variable that combines both names with a space.
3. Use template literals (`` ` ``) to print "Hello, [full name]".

let firstName = "Ali";
let lastName = "Mohammed";

let fullName = firstName + " " + lastName;

console.log(`Hello, ${fullName}`);

Create a function named `greet`:

1. It takes one parameter called `name`.
2. It returns the string "Hello, [name]!".
3. Call the function with the name "Sarah" and log the result.

function greet(name) {
    return "Hello, " + name + "!";
}

console.log(greet("Sarah")); // Hello, Sarah!

What are the results (true/false)? Write code to verify:

1. Is `5 == "5"` (value equality)?
2. Is `5 === "5"` (value and type equality)?
3. Is `10 > 5` and `5 < 2` (use AND `&&`)?

console.log(5 == "5");   // true
console.log(5 === "5");  // false
console.log(10 > 5 && 5 < 2); // false (second condition is false)

Create an object that represents a car:

1. Include the properties: `brand` (Toyota), `model` (Corolla), `year` (2020).
2. Change `year` to 2022.
3. Print "My car is [brand] [model]" using the object properties.

let car = {
    brand: "Toyota",
    model: "Corolla",
    year: 2020
};

car.year = 2022;

console.log(`My car is ${car.brand} ${car.model}`);

Work with a list of colors:

1. Create an array `colors` with: "Red", "Green", "Blue".
2. Print the first element of the array.
3. Add a new color "Yellow" to the end of the array (push).
4. Print the array length.

let colors = ["Red", "Green", "Blue"];

console.log(colors[0]); // Red

colors.push("Yellow");

console.log(colors.length); // 4

Use shorthand operators to update a variable:

1. Define `score` with the value 10.
2. Add 5 to `score` using `+=`.
3. Multiply `score` by 2 using `*=`.
4. Decrement `score` by 1 using `--`.

let score = 10;

score += 5; // now 15
score *= 2; // now 30
score--;    // now 29

console.log(score);

Do the following:

1. Write a single-line comment.
2. Write a multi-line comment.
3. Use `console.error()` to print a fake error message "Something went wrong".
4. Use `console.warn()` to print a warning "Be careful".

// This is a single-line comment

/*
  This is a
  multi-line comment
*/

console.error("Something went wrong");
console.warn("Be careful");