feat: add number to Roman numeral conversion

Conversions/NumberToRoman.js

@@ -0,0 +1,43 @@
+/**
+ * @function numberToRoman
+ * @description Converts a decimal number to its Roman numeral representation.
+ * @param {number} num - A positive integer between 1 and 3999
+ * @returns {string} - The Roman numeral representation
+ * @see https://en.wikipedia.org/wiki/Roman_numerals
+ * @example numberToRoman(3) => "III"
+ * @example numberToRoman(9) => "IX"
+ * @example numberToRoman(58) => "LVIII"
+ * @example numberToRoman(1994) => "MCMXCIV"
+ */
+const numberToRoman = (num) => {
+  if (!Number.isInteger(num) || num < 1 || num > 3999) {
+    throw new TypeError('Input must be an integer between 1 and 3999')
+  }
+  const values = [1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1]
+  const symbols = [
+    'M',
+    'CM',
+    'D',
+    'CD',
+    'C',
+    'XC',
+    'L',
+    'XL',
+    'X',
+    'IX',
+    'V',
+    'IV',
+    'I'
+  ]
+  let result = ''
+  let remaining = num
+  for (let i = 0; i < values.length; i++) {
+    while (remaining >= values[i]) {
+      result += symbols[i]
+      remaining -= values[i]
+    }
+  }
+  return result
+}
+
+export { numberToRoman }

Conversions/test/NumberToRoman.test.js

@@ -0,0 +1,47 @@
+import { numberToRoman } from '../NumberToRoman.js'
+
+describe('numberToRoman', () => {
+  test("numberToRoman(1) returns 'I'", () => {
+    expect(numberToRoman(1)).toBe('I')
+  })
+
+  test("numberToRoman(3) returns 'III'", () => {
+    expect(numberToRoman(3)).toBe('III')
+  })
+
+  test("numberToRoman(4) returns 'IV'", () => {
+    expect(numberToRoman(4)).toBe('IV')
+  })
+
+  test("numberToRoman(9) returns 'IX'", () => {
+    expect(numberToRoman(9)).toBe('IX')
+  })
+
+  test("numberToRoman(40) returns 'XL'", () => {
+    expect(numberToRoman(40)).toBe('XL')
+  })
+
+  test("numberToRoman(58) returns 'LVIII'", () => {
+    expect(numberToRoman(58)).toBe('LVIII')
+  })
+
+  test("numberToRoman(1994) returns 'MCMXCIV'", () => {
+    expect(numberToRoman(1994)).toBe('MCMXCIV')
+  })
+
+  test("numberToRoman(3999) returns 'MMMCMXCIX'", () => {
+    expect(numberToRoman(3999)).toBe('MMMCMXCIX')
+  })
+
+  test('throws TypeError for 0', () => {
+    expect(() => numberToRoman(0)).toThrow(TypeError)
+  })
+
+  test('throws TypeError for 4000', () => {
+    expect(() => numberToRoman(4000)).toThrow(TypeError)
+  })
+
+  test('throws TypeError for float', () => {
+    expect(() => numberToRoman(1.5)).toThrow(TypeError)
+  })
+})