---
title: Roman Numeral Converter
---
 Remember to use <a>**`Read-Search-Ask`**</a> if you get stuck. Try to pair program  and write your own code 
###  Problem Explanation:
You will create a program that converts an integer to a Roman Numeral.
#### Relevant Links
* <a href='http://www.mathsisfun.com/roman-numerals.html' target='_blank' rel='nofollow'>Roman Numerals</a>
* <a href='http://forum.freecodecamp.com/t/javascript-array-prototype-splice/14307' target='_blank' rel='nofollow'>Array.splice()</a>
* <a href='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/indexOf' target='_blank' rel='nofollow'>Array.indexOf()</a>
* <a href='http://forum.freecodecamp.com/t/javascript-array-prototype-join/14292' target='_blank' rel='nofollow'>Array.join()</a>
##  Hint: 1
Creating two arrays, one with the Roman Numerals and one with the decimal equivalent for the new forms will be very helpful.
> _try to solve the problem now_
##  Hint: 2
If you add the numbers to the arrays that go before the new letter is introduced, like values for 4, 9, and 40, it will save you plenty of code.
> _try to solve the problem now_
##  Hint: 3
You can't have more than three consecutive Roman numerals together.
> _try to solve the problem now_
## Spoiler Alert!
**Solution ahead!**
##  Basic Code Solution:
var convertToRoman = function(num) {
var decimalValue = [ 1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1 ];
var romanNumeral = [ 'M', 'CM', 'D', 'CD', 'C', 'XC', 'L', 'XL', 'X', 'IX', 'V', 'IV', 'I' ];
var romanized = '';
for (var index = 0; index < decimalValue.length; index++) {
while (decimalValue[index] <= num) {
romanized += romanNumeral[index];
num -= decimalValue[index];
}
}
return romanized;
}
// test here
convertToRoman(36);
 <a href='https://repl.it/CLmf/0' target='_blank' rel='nofollow'>Run Code</a>
### Code Explanation:
* We start off by creating two arrays with default conversion with matching indices. These are called `decimalValue` and `romanNumeral`. We also create an empty string variable, `romanized`, which will house the final roman number.
* Using a for loop, we loop through the indicies of the `decimalValue` array. We continue to loop until while the value at the current `index` will fit into `num`.
* Next, we add the roman numeral and decrease `num` by the decimal equivalent.
* Finally, we return the value of `romanized`.
#### Relevant Links
* <a href='http://forum.freecodecamp.com/t/javascript-for-loop/14666' target='_blank' rel='nofollow'>For Loops</a>
* <a>While Loops</a>
##  Intermediate Code Solution:
function convertToRoman(num) {
var romans = ["I", "V", "X", "L", "C", "D", "M"],
ints = [],
romanNumber = [],
numeral = "";
while (num) {
ints.push(num % 10);
num = Math.floor(num/10);
}
for (i=0; i<ints.length; i++){
units(ints[i]);
}
function units(){
numeral = romans[i*2];
switch(ints[i]) {
case 1:
romanNumber.push(numeral);
break;
case 2:
romanNumber.push(numeral.concat(numeral));
break;
case 3:
romanNumber.push(numeral.concat(numeral).concat(numeral));
break;
case 4:
romanNumber.push(numeral.concat(romans[(i*2)+1]));
break;
case 5:
romanNumber.push(romans[(i*2)+1]);
break;
case 6:
romanNumber.push(romans[(i*2)+1].concat(numeral));
break;
case 7:
romanNumber.push(romans[(i*2)+1].concat(numeral).concat(numeral));
break;
case 8:
romanNumber.push(romans[(i*2)+1].concat(numeral).concat(numeral).concat(numeral));
break;
case 9:
romanNumber.push(romans[i*2].concat(romans[(i*2)+2]));
}
}
return romanNumber.reverse().join("").toString();
}
// test here
convertToRoman(97);
 <a href='https://repl.it/C1YV' target='_blank' rel='nofollow'>Run Code</a>
### Code Explanation:
* Create an array of Roman Numerals (`romans`).
* Use a for loop to create an array of the digits (`ints`) in the number.
* Loop through the array of digits (base 10) and as you do, increment the Roman Numeral (base 5) index by 2 (`numeral = romans[i*2]`).
* Within the loop, use Switch Case to push the proper Roman Numerals (backwards) onto that array.
* Reverse the Roman Numerals array and turn it into a string.
#### Relevant Links
* <a href='http://forum.freecodecamp.com/t/javascript-for-loop/14666' target='_blank' rel='nofollow'>For Loops</a>
* <a>While Loops</a>
* <a href='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math' target='_blank' rel='nofollow'>Math</a>
##  Intermediate Code Solution:
function convertToRoman(num) {
var romans = [
// 10^i 10^i*5
["I", "V"], // 10^0
["X", "L"], // 10^1
["C", "D"], // 10^2
["M"] // 10^3
],
digits = num.toString()
.split('')
.reverse()
.map(function(item, index) {
return parseInt(item);
}),
numeral = "";
// Loop through each digit, starting with the ones place
for (var i=0; i<digits.length; i++) {
// Make a Roman numeral that ignores 5-multiples and shortening rules
numeral = romans[i][0].repeat(digits[i]) + numeral;
// Check for a Roman numeral 5-multiple version
if (romans[i][1]) {
numeral = numeral
// Change occurrences of 5 * 10^i to the corresponding 5-multiple Roman numeral
.replace(romans[i][0].repeat(5), romans[i][1])
// Shorten occurrences of 9 * 10^i
.replace(romans[i][1] + romans[i][0].repeat(4), romans[i][0] + romans[i+1][0])
// Shorten occurrences of 4 * 10^i
.replace(romans[i][0].repeat(4), romans[i][0] + romans[i][1]);
}
}
return numeral;
}
// test here
convertToRoman(36);
 <a href='https://repl.it/C1YV' target='_blank' rel='nofollow'>Run Code</a>
### Code Explanation:
* Use an array (`romans`) to create a matrix containing the Roman numeral for a given power of 10 and, if available, the Roman numeral for that power of 10 times 5.
* Convert the input number (`num`) to a reversed array of digits (`digits`) so that we can loop through those digits starting with the ones position and going up.
* Loop through each digit, starting with the ones place, and create a Roman numeral string by adding each higher-power Roman numeral to the start of the `numeral` string a number of times equal to `digit`. This initial string ignores the Roman numerals that are a power of 10 times 5 and also ignores shortening rules.
* If the relevant power of 10 has a 5-multiple Roman numeral, in `numeral`, replace 5-in-a-row occurrences with the relevant 5-multiple Roman numeral (i.e., V, L, or D) and shorten occurrences of 9 * 10^i (e.g., VIIII to VIX) and 4 * 10^i (e.g., XXXX to XL). Order is important here!
* Finally, return `numeral`.
#### Relevant Links
* <a href='http://forum.freecodecamp.com/t/javascript-for-loop/14666' target='_blank' rel='nofollow'>For Loops</a>
* <a href='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/split' target='_blank' rel='nofollow'>.split()</a>
* <a href='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/reverse' target='_blank' rel='nofollow'>.reverse()</a>
* <a href='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/map' target='_blank' rel='nofollow'>.map()</a>
* <a href='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/toString' target='_blank' rel='nofollow'>.toString()</a>
* <a href='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/parseInt' target='_blank' rel='nofollow'>parseInt()</a>
* <a href='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/replace' target='_blank' rel='nofollow'>.replace()</a>
* <a href='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/repeat' target='_blank' rel='nofollow'>.repeat()</a>
##  NOTES FOR CONTRIBUTIONS:
*  **DO NOT** add solutions that are similar to any existing solutions. If you think it is **_similar but better_**, then try to merge (or replace) the existing similar solution.
* Add an explanation of your solution.
* Categorize the solution in one of the following categories — **Basic**, **Intermediate** and **Advanced**. 
* Please add your username only if you have added any **relevant main contents**. ( **_DO NOT_** _remove any existing usernames_)
> See  <a href='http://forum.freecodecamp.com/t/algorithm-article-template/14272' target='_blank' rel='nofollow'>**`Wiki Challenge Solution Template`**</a> for reference.