Roman Numeral Converter - The Easy Way!

[kuklin_artem]

So while I was solving the Roman Numeral Converter Challenge I have come upon what I consider an important realisation (for me atleast).

You can find this challenge here:
Roman Numerals

So what I realised is that I don’t really have to make a converter. I just need an object that holds the valus of roman numerals for Units, Tens, Hundreds and Thousands…

Should I desire to convert Tens-of-Thousands or more, I will simply add another property that holds the value for each Ten-Thousand.
Since each value (unit, ten, hundred…) is represented with an integer from 0-9, I can just pull the corresponding roman numeral from romanObj.

I was kind of shocked that I couldn’t find this solution… After all, it is easy to maintain and understand.

Here is my code:

function convertToRoman(num) {
  let romanArr = [];
  const romanObj = {
    0: ["","I","II","III","IV","V","VI","VII","VIII","IX"],
    1: ["","X","XX","XXX","XL","L","LX","LXX","LXXX","XC"],
    2: ["","C","CC","CCC","CD","D","DC","DCC","DCCC","CM"],
    3: ["","M","MM","MMM","MV","V","VM","VMM","VMMM","IX"]
  }
  const numArrRep = num.toString().split("").map(item => parseInt(item));
  let m = numArrRep.length - 1;
  for(let n = m; n >= 0; n--) {
    romanArr.push(romanObj[n][numArrRep[m - n]]);
  }
 return romanArr.join("");
}

convertToRoman(3999);

What would you say the drawbacks of such an approach would be?

[jwilkins.oboe]

HI @kuklin_artem !

I added spoiler tags around your code for those who have not worked on this challenge yet.
I also moved this to the javascript section since this is more of a algorithm challenge than an actual project per se.

[jsdisco]

How would your code handle convertToRoman(4000)?

[ILM]

it works because the challenge is for numbers up to 3999, but it’s not correct

note that MV is NOT 4000, and is not a valid roman character at all
V is not 5000, IX is not 9000

for that to be correct you need to have a dash above them (which I think is why they are not requested.

4000 is I̅V̅
5000 is V̅
6000 is V̅I̅
7000 is V̅I̅I̅
8000 is V̅I̅I̅I̅
9000 is I̅X̅

[lawrencek1992]

I wrote functions for each place value a number might have (ones, tens, hundreds, and thousands) which used switch statements to convert each place value into its roman numeral equivalent. Then I used a series of ternary statements to evaluate the length of the number and decide which place value functions were necessary to use. Yours is much cleaner. I like it. I think I suffer from excessively long code, because I get stubborn about wanting to make something work.

Also glad to know that I shouldn’t feel bad for writing a converter that can’t handle numbers greater than 3,999.

[kuklin_artem]

That is a valid point, thanks for spotting it. I did leave out the vinculum. Please allow me to correct this.
Here is the correct code:

function convertToRoman(num) {
  let romanArr = [];
  const romanObj = {
    0: ["","I","II","III","IV","V","VI","VII","VIII","IX"],
    1: ["","X","XX","XXX","XL","L","LX","LXX","LXXX","XC"],
    2: ["","C","CC","CCC","CD","D","DC","DCC","DCCC","CM"],
    3: ["","M","MM","MMM","I̅V̅","V̅","V̅I̅","V̅I̅I̅","V̅I̅I̅I̅","I̅X̅"]
  }
  const numArrRep = num.toString().split("").map(item => parseInt(item));
  let m = numArrRep.length - 1;
  for(let n = m; n >= 0; n--) {
    romanArr.push(romanObj[n][numArrRep[m - n]]);
  }
 return romanArr.join("");
}

convertToRoman(5012);

Oh, will there be any problems using “non-standard” characters in code out in the real world?
I can remember having to switch the encoding in WIndosw 95-98 back when I was a kid. I assume that programmers nowadays are more aware of different encoding needs for different purposes…

[kuklin_artem]

I though of going the same route as you, but the potential length of the code dissuaded me. Plus I am the kind of person the alwsay manages to spell something wrong.
ANd keeping in mind how JS is case sensitive, I definitly would have spent some time searching for one typo.

[cherylm]

I used place values and about 20 if statements. My code is probably fifty lines.

It also bugged me a little that it only went up to 3999. I never knew that was the highest number in the Roman numeral system.

[pahbloo]

Here is my solution, very similar to yours, but i used a bi-dimensional array. BTW, it just correctly converts numbers up to 3999:

function convertToRoman(num) {
  if (num >= 4000) return;

  const roman = ` M MM MMM
 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`
    .split("\n")
    .map((el) => el.split(" "));

  return num
    .toString()
    .padStart(4, 0)
    .split("")
    .map((digit, index) => roman[index][digit])
    .join("");
}