JS: format number the hard way

format_number.js

/**
 * format a number to look like "12.300 Mio." (german format)
 *
 * Spec:
 * * numbers equal or larger than 100000 are suffixed with "Mio.".
 * * three significant digits
 * * dots after each 3 consecutive digits
 *
 * Why not use .toPrecision() alone? Because it might end up in
 * "scientific notation" (1.23e9). Yeah, that makes sence, JS!
 *
 * @param Number num the number to format
 * @return String the formatted representation
 * @see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/toPrecision
 */
function format_number(num) {
    var append = "";
    if (num > 99999) {
        append = " Mio.";
        num /= 1e6;
    }
    return (+num.toPrecision(3)).toString()
        .replace('.', ',')
        .replace(/\B(?=(\d{3})+(?!\d))/g, ".") + append;
}