Roman Number Converter Using Javascript

Javascript 

Number to Roman convert:

function toroman (num) {
if (!+num)
return false;
var digits = String(+num).split(""),
key = ["","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"],
roman = "",

i = 3;
while (i--)
roman = (key[+digits.pop() + (i * 10)] || "") + roman;
return Array(+digits.join("") + 1).join("M") + roman;
}

Roman to Number convert:

function tonumber (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;
}