Javascript str_pad of zeroes

/************************************
var number, str, ndigits;

ndigits = 5;    // you want it to have 5 digits
number = 23;    // this is your number
str = digits(number, ndigits); // str == '00023'       this is your result

number = 936;
ndigits = 10;
str = digits(number, ndigits); // str == '0000000936'
************************************/

function digits(n,ndigit){
    return (n.length < ndigit ? digits("0"+n, ndigit) : n);
}