src/roman-to-integer/res.js

/**
 * From the following table, find the highest roman numeral (n) with the highest decimal value (v)
 * that is taken from the left part of the roman numeral r
 *
 * From http://www.rapidtables.com/convert/number/how-roman-numerals-to-number.htm
 * 
 * I	1
 * IV	4
 * V	5
 * IX	9
 * X	10
 * XL	40
 * L	50
 * XC	90
 * C	100
 * CD	400
 * D	500
 * CM	900
 * M	1000
 * res.js
 * @authors Your Name (you@example.org)
 * @date    2017-02-21 22:06:00
 * @version $Id$
 */

/**
 * @param {string} s
 * @return {number}
 */
var romanToInt = function(s) {
	let res = 0;
    while (s) {
        if (s.indexOf('M') === 0) {
        	res += 1000;
        	s = s.substring(1);
        } else if (s.indexOf('CM') === 0) {
        	res += 900;
        	s = s.substring(2);
        } else if (s.indexOf('D') === 0) {
        	res += 500;
        	s = s.substring(1);
        } else if (s.indexOf('CD') === 0) {
        	res += 400;
        	s = s.substring(2);
        } else if (s.indexOf('C') === 0) {
        	res += 100;
        	s = s.substring(1);
        } else if (s.indexOf('XC') === 0) {
        	res += 90;
        	s = s.substring(2);
        } else if (s.indexOf('L') === 0) {
        	res += 50;
        	s = s.substring(1);
        } else if (s.indexOf('XL') === 0) {
        	res += 40;
        	s = s.substring(2);
        } else if (s.indexOf('X') === 0) {
        	res += 10;
        	s = s.substring(1);
        } else if (s.indexOf('IX') === 0) {
        	res += 9;
        	s = s.substring(2);
        } else if (s.indexOf('V') === 0) {
        	res += 5;
        	s = s.substring(1);
        } else if (s.indexOf('IV') === 0) {
        	res += 4;
        	s = s.substring(2);
        } else if (s.indexOf('I') === 0) {
        	res += 1;
        	s = s.substring(1);
        }
    }

    return res;
};