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# MarcSymonds/ConvertToRomanNumerals.js

Created April 25, 2017 08:42
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JavaScript.Example - Convert a number to Roman numerals. Only works effectively up to 9999.
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 function convertToRoman(num) { var romanNumerals = [ {number: 1, numeral: "I", sub: 0}, {number: 5, numeral: "V", sub: -1}, {number: 10, numeral: "X", sub: -2}, {number: 50, numeral: "L", sub: -1}, {number: 100, numeral: "C", sub: -2}, {number: 500, numeral: "D", sub: -1}, {number: 1000, numeral: "M", sub: -2} ]; var rni = romanNumerals.length - 1; var result = ""; var rn, rnx; while (num > 0 && rni >= 0) { rn = romanNumerals[rni]; while (num >= rn.number) { result += rn.numeral; num -= rn.number; } // Symbols are placed from left to right in order of value, starting // with the largest. However, in a few specific cases, to avoid four // characters being repeated in succession (such as IIII or XXXX), // subtractive notation is used where two symbols are used which // indicate a smaller number being subtracted from a larger number; // for example, 900 is represented as CM, which means 100 subtracted // from 1000. if (rn.sub !== 0) { rnj = rni + rn.sub; rnx = romanNumerals[rnj]; if (num >= (rn.number - rnx.number)) { result = result + rnx.numeral + rn.numeral; num -= (rn.number - rnx.number); } } --rni; } return result; }
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 // A longer, but more direct approach. function convertToRoman(num) { var result = ""; while (num >= 1000) { result += "M"; num -= 1000; } if (num >= 900) { result += "CM"; num -= 900; } if (num >= 500) { result += "D"; num -= 500; } if (num >= 400) { result += "DC"; num -= 400; } while (num >= 100) { result += "C"; num -= 100; } if (num >= 90) { result += "XC"; num -= 90; } if (num >= 50) { result += "L"; num -= 50; } if (num >= 40) { result += "XL"; num -= 40; } while (num > 10) { result += "X"; num -= 10; } if (num == 9) { result += "IX"; num -= 9; } if (num >= 5) { result += "V"; num -= 5; } if (num == 4) { result += "IV"; num -= 4; } while (num > 0) { result += "I"; num--; } return result; }