Accepts a number and returns the corresponding roman numeral.

romanize.js

var romanize = function(num) {
    var rom = {
        M: 1000,
        CM: 900,
        D: 500,
        CD: 400,
        C: 100,
        XC: 90,
        L: 50,
        XL: 40,
        X: 10,
        IX: 9,
        V: 5,
        IV: 4,
        I: 1
    };
    return Object.keys(rom).reduce(function(acc, ch) {
        acc.str += ch.repeat(acc.num / rom[ch]);
        acc.num %= rom[ch];
        return acc;
    }, {
        str: '',
        num: num
    }).str;
};