chore: merge "Added DecimalToRoman" (TheAlgorithms#707)

* Added DecimalToRoman

* add explanation

* added test

Author: beam41

Conversions/DecimalToRoman.js

@@ -0,0 +1,52 @@
+/*
+    Decimal To Roman
+
+    This algorithm take decimal number and convert to roman numeral according to standard form (https://en.wikipedia.org/wiki/Roman_numerals#Description)
+
+    Algorithm & Explanation : https://www.rapidtables.com/convert/number/how-number-to-roman-numerals.html
+*/
+
+const values = {
+  M: 1000,
+  CM: 900,
+  D: 500,
+  CD: 400,
+  C: 100,
+  XC: 90,
+  L: 50,
+  XL: 40,
+  X: 10,
+  IX: 9,
+  V: 5,
+  IV: 4,
+  I: 1
+}
+
+const orders = [
+  'M',
+  'CM',
+  'D',
+  'CD',
+  'C',
+  'XC',
+  'L',
+  'XL',
+  'X',
+  'IX',
+  'V',
+  'IV',
+  'I'
+]
+
+function decimalToRoman (num) {
+  let roman = ''
+  for (var symbol of orders) {
+    while (num >= values[symbol]) {
+      roman += symbol
+      num -= values[symbol]
+    }
+  }
+  return roman
+}
+
+export { decimalToRoman }

Conversions/test/DecimalToRoman.test.js

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+import { decimalToRoman } from '../DecimalToRoman'
+
+describe('decimalToRoman', () => {
+  it('expects to return correct roman numeral of given number', () => {
+    expect(decimalToRoman(34)).toBe('XXXIV')
+  })
+  it('expects to return correct roman numeral of given number', () => {
+    expect(decimalToRoman(28)).toBe('XXVIII')
+  })
+  it('expects to return correct roman numeral of given number', () => {
+    expect(decimalToRoman(2021)).toBe('MMXXI')
+  })
+})