Miles to Kilometers - FreeCodeCamp Daily Challenge

Miles to Kilometers Conversion: A Classic Algorithm Problem

Today we tackle FreeCodeCamp’s daily challenge: convert a given distance in miles to its equivalent in kilometers, rounding the result to two decimal places. These exercises help us practice mathematical operations and decimal number manipulation.

Problem Statement

Given a distance in miles (non-negative number), return the equivalent distance in kilometers. 1 mile equals 1.60934 kilometers. Round the result to two decimal places.

Examples

Approach & Analysis

The key is to apply the conversion rate correctly and round the result. The process can be summarized in three steps:

1. Multiply the number of miles by 1.60934.
2. Round the result to two decimal places.
3. Return the final value.

Why are these exercises useful?

• Reinforces basic arithmetic operations.
• Practices rounding and formatting decimal numbers.

JavaScript Implementation

Let’s translate this process into code:

function convertToKm(miles) {
  const kilometersPerMile = 1.60934
  let result = miles * kilometersPerMile
  result = Number.parseFloat(result.toFixed(2))
  return result
}

Step-by-step Explanation

• The constant kilometersPerMile is declared for clarity and maintainability.
• The input is multiplied by the conversion rate.
• toFixed(2) is used to round to two decimals, and parseFloat returns a number.

Complexity Analysis

The function performs simple arithmetic and rounding:

Space complexity is also $O(1)$, as no additional structures are used.

Edge Cases & Considerations

• If the input is 0, the result is 0.
• If the input is a decimal, conversion and rounding work correctly.
• Negative or non-numeric inputs are not handled, as the statement guarantees valid inputs.

Reflections & Learnings

• Importance of declaring constants for conversion rates.
• Correct use of rounding functions.
• Validating test cases and edge cases.

Resources & References

• MDN: Number.prototype.toFixed()
• Unit conversion on Wikipedia