Practice Problems

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: Convert Kilometers to Miles

Objective: Write a function that converts kilometers to miles.

Instructions:

Define the Function:
- Create a function named convertKilometersToMiles that takes one parameter kilometers.
Calculate Miles:
- Inside the function, convert the kilometers value to miles using the conversion rate 1 kilometer = 0.621371 miles.
Return the Result:
- The function should return the calculated miles.
Invoke the Function:
- Call the convertKilometersToMiles function with a sample value and log the result to the console.

Problem 2: Sum of Numbers in an Array

Objective: Create a function that takes an array of numbers and returns their sum.

Instructions:

Define the Function:
- Create a function named sumArray that takes one parameter numbers (an array of numbers).
Calculate the Sum:
- Inside the function, iterate through the numbers array and calculate the total sum.
Return the Sum:
- The function should return the total sum of the numbers.
Invoke the Function:
- Call the sumArray function with a sample array and log the result to the console.

Problem 3: Calculate the Area of a Circle

Objective: Write a function that calculates the area of a circle given its radius.

Instructions:

Define the Function:
- Create a function named calculateCircleArea that takes one parameter radius.
Compute the Area:
- Use the formula Area = π * radius * radius to calculate the area.
Return the Area:
- The function should return the calculated area.
Invoke the Function:
- Call the calculateCircleArea function with a sample radius and log the result to the console.

ADVANCE PROBLEMS

Problem 4: Currency Converter with Default Parameter

Objective:

Write a function that converts an amount in US dollars to another currency, defaulting to Euros if no currency code is provided.

Instructions:

Define the Function

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function convertCurrency(amountUSD, toCurrency = "EUR") {
  // …
}

Implementation Steps
- Inside, use a simple fixed conversion rate:
  - USD → EUR: multiply by 0.85
  - USD → GBP: multiply by 0.75
  - USD → JPY: multiply by 110
- If toCurrency is not one of these three codes, return "Unsupported currency".
Return Value
- If supported, return the converted amount, rounded to two decimals.
- Otherwise, return the unsupported message.
Examples

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console.log(convertCurrency(100));           // defaults to EUR: e.g. "85.00 EUR"
console.log(convertCurrency(100, "GBP"));    // "75.00 GBP"
console.log(convertCurrency(100, "AUD"));    // "Unsupported currency"

Problem 5: Swap Two Values

Objective:

Create a function that takes two arguments and returns them in swapped order.

Instructions:

Define the Function

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function swap(a, b) {
  // …
}

Implementation Steps
- Inside, return an array or object that places b first, then a.
Return Value
- As an array: [b, a]
- Or as an object: { first: b, second: a }
Examples

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console.log(swap(1, 2));       // [2, 1]
console.log(swap("x", "y"));   // ["y", "x"]

Problem 6: Merge and Deduplicate Arrays

Objective:

Write a function that accepts two arrays, merges them, and returns a new array with only unique values.

Instructions:

Define the Function

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function mergeUnique(arr1, arr2) {
  // …
}

Implementation Steps
- Combine the two arrays into one (e.g., using concat).
- Iterate through the combined array, and build a new array that only includes each value once (check with includes).
Return Value
- The deduplicated array.
Examples

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console.log(mergeUnique([1,2,3], [2,3,4]));      // [1,2,3,4]
console.log(mergeUnique(["a","b"], ["b","c"])); // ["a","b","c"]

Day 12: Function Parameters and Return Values