Convert Roman Numbers to Decimal Numbers in JavaScript

For converting a Roman numeral into a decimal number, JavaScript provides simple and efficient ways. Roman numerals are a number system that started in ancient Rome and are still used today in different situations. Converting Roman numerals to decimal (integer) values can be useful in many applications, such as date conversions, numbering systems, or educational tools. In this article, we will see a JavaScript algorithm to convert Roman numerals into decimal numbers efficiently.

Understanding Roman Numerals

Roman numerals are a Number System that uses combinations of letters from the Latin alphabet to represent values. It uses seven letters to represent values:

Roman numerals follow specific rules:

• Numbers are usually written from largest to smallest, going from left to right.
• If a smaller number comes before a larger one, it represents subtraction (e.g., IV = 4).
• You can't use the same symbol more than three times in a row.

JavaScript Algorithm for Conversion

To convert a Roman numeral into a decimal number, we can follow the steps mentioned below:

• Create a mapping object of Roman numeral symbols to their integer values.
• Loop through the input string character by character.
• If the current numeral is smaller than the next numeral, subtract its value.
• Otherwise, add its value to the total.

JavaScript Code Implementation

The following is a simple code implementation for converting roman numerals into decimal number.

function romanToDecimal(roman) {
    const romanValues = {
        'I': 1, 'V': 5, 'X': 10, 'L': 50, 'C': 100, 'D': 500, 'M': 1000
    };
    let total = 0;

    for (let i = 0; i < roman.length; i++) {
        const current = romanValues[roman[i]];
        const next = romanValues[roman[i + 1]];
        
        if (next && current < next) {
            total -= current;
        } else {
            total += current;
        }
    }
    
    return total;
}

// Example usage
console.log(romanToDecimal("XII"));

Output

12

Code Explanation

In the above code, we have successfully implemented a JavaScript algorithm for converting Roman numerals into decimal numbers. Here is the code explanation:

• We have created an object roman Values that maps each Roman numeral to its corresponding decimal value.
• Then, we have initialize total to store the final integer result.
• We iterate over the string, checking if the current character represents a value smaller than the next one.
• If current precedes next, we subtract it (e.g., in "IX", I is subtracted because it precedes X).
• If current doesn't precedes next, we add the value to the total.
• Finally, we return the computed decimal value.

Complexity

This algorithm runs in O(n) time complexity, where n is the length of the input Roman numeral string.

Conclusion

In this article, we have created a simple JavaScript function that efficiently converts the Roman numerals into decimal numbers. By using this simple JavaScript function, you can quickly convert Roman numerals into regular numbers. This method is efficient and follows the basic rules of Roman numerals. Overall, this algorithm is a great starting point for working with Roman numerals in JavaScript.