JavaScript: Convert an integer into a Roman Numeral

Last update on March 01 2025 11:04:18 (UTC/GMT +8 hours)

JavaScript Math: Exercise-21 with Solution

Integer to Roman Numeral Conversion

Write a JavaScript function that converts an integer into a Roman numeral.

Sample Solution:

Visual Presentation:

$JavaScript: Math - Convert an integer into a Roman Numeral.$

JavaScript Code:

// Define a function named integer_to_roman that converts an integer to its Roman numeral representation.
function integer_to_roman(num) {
    // Check if num is not a number, if so, return false.
    if (typeof num !== 'number') 
        return false; 

    // Split the digits of num and store them in an array.
    var digits = String(+num).split(""),
    // Define an array representing Roman numeral symbols for different place values.
    key = ["","C","CC","CCC","CD","D","DC","DCC","DCCC","CM",
           "","X","XX","XXX","XL","L","LX","LXX","LXXX","XC",
           "","I","II","III","IV","V","VI","VII","VIII","IX"],
    // Initialize an empty string to store the Roman numeral.
    roman_num = "",
    // Set a counter to determine the place value (ones, tens, hundreds, etc.).
    i = 3;
    // Iterate through the digits array to construct the Roman numeral representation.
    while (i--)
        roman_num = (key[+digits.pop() + (i * 10)] || "") + roman_num;
    // Add 'M' symbols for the thousands place.
    return Array(+digits.join("") + 1).join("M") + roman_num;
}

// Output the Roman numeral representation of the integer 27 to the console.
console.log(integer_to_roman(27));

Output:

XXVII

Flowchart:

$Flowchart: JavaScript Math- Convert an integer into a Roman Numeral$

Live Demo:

For more Practice: Solve these Related Problems:

Write a JavaScript function that converts an integer to a Roman numeral using iterative subtraction with mapping.
Write a JavaScript function that recursively converts an integer to its Roman numeral representation.
Write a JavaScript function that implements a mapping of decimal values to Roman symbols and assembles the numeral accordingly.
Write a JavaScript function that converts an integer to a Roman numeral and validates that the number is within 1 to 3999.

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