Below are three quick problems to help you apply what you learned. Create a new JavaScript file for each problem to practice building from scratch.

Problem 1: Greet User by Name

Objective: Write a function that greets a user by name.

Instructions:

Define the Function:
- Create a function named greetUser that takes one parameter name.
Return Greeting:
- The function should return a greeting message that includes the provided name.
Invoke the Function:
- Call the greetUser function with a sample name and log the result to the console.

Problem 2: Calculate Area of a Rectangle

Objective: Create a function that calculates the area of a rectangle given its length and width.

Instructions:

Define the Function:
- Create a function named calculateArea that takes two parameters: length and width.
Compute Area:
- The function should return the area by multiplying length by width.
Invoke the Function:
- Call the calculateArea function with sample length and width values and log the result to the console.

Problem 3: Sum of Two Numbers

Objective: Write a function that takes two numbers as parameters and returns their sum.

Instructions:

Define the Function:
- Create a function named addNumbers that takes two parameters: num1 and num2.
Return Sum:
- The function should return the sum of num1 and num2.
Invoke the Function:
- Call the addNumbers function with sample numbers and log the result to the console.

Objective:

Create a function that accepts any number of numeric arguments (using rest parameters) and returns an object containing basic statistics.

Instructions:

function getStats(...nums) { /* … */ }

Compute Metrics
- count: the number of inputs.
- sum: total of all values.
- min and max: smallest and largest values.
- average: sum / count.
Return Value
The function should return an object:

{
  count: 5,
  sum: 42,
  min: 3,
  max: 10,
  average: 8.4
}

Objective:

Write a function that takes a single-word string and returns it in “title case” (first letter uppercase, the rest lowercase).

Instructions:

js
Copy
function toTitleCase(word) {
  // …
}

Implementation Steps
- Ensure the input is treated as a string.
- Extract the first character, convert it to uppercase.
- Extract the remainder of the string, convert it to lowercase.
- Concatenate and return the result.
Examples

js
Copy
console.log(toTitleCase("javascript")); // "Javascript"
console.log(toTitleCase("hELLo"));      // "Hello"

Objective:

Create a function that calculates the factorial of a non-negative integer using recursion.

Instructions:

js
function factorial(n) {
  // …
}

Implementation Logic
- If n is 0 or 1, return 1 (base case).
- Otherwise return n * factorial(n - 1).
Examples

js
console.log(factorial(0)); // 1
console.log(factorial(5)); // 120  (5×4×3×2×1)
console.log(factorial(7)); // 5040

Day 11: Defining and Invoking Functions