roman numerals kata

'use strict';

function convertDigit(val, one, five, ten) {
	if (val !== '' && val !== undefined && val !== '0') {
		val = parseInt(val);
		if (val < 4) {
			return one.repeat(val);
		} else if (val <= 5) {
			return one.repeat(5 - val) + five;
		} else if (val < 9) {
			return five + one.repeat(val - 5);
		} else {
			return one.repeat(10 - val) + ten;
		}
	}
	return '';
}

module.exports = {
	toRoman: function (val) {
		val = ('' + val).split('').reverse().join('');
		return convertDigit(val[2], 'C', 'D', 'M') + 
			convertDigit(val[1], 'X', 'L', 'C') + 
			convertDigit(val[0], 'I', 'V', 'X')
	}
}