Accepts a roman numeral and returns the corresponding integer.

deromanize.js

var deromanize = function(str) {
    var str = str.toUpperCase(),
        validator = /^M*(?:D?C{0,3}|C[MD])(?:L?X{0,3}|X[CL])(?:V?I{0,3}|I[XV])$/,
        token = /[MDLV]|C[MD]?|X[CL]?|I[XV]?/g,
        key = {
            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
        },
        num = 0, m;
    if (!(str && validator.test(str))) {
        return false;
    }
    while (m = token.exec(str)) {
        num += key[m[0]];
    }
    return num;
};