Format numbers to human-readable format and money format (Euro, but easily adaptable)

numberformat.js

if (!Number.prototype.format) {
    Number.prototype.format = function(decimals, decimal_separator, thousands_separator, prefix, suffix) {
        decimals = decimals || 0;
        decimal_separator = decimal_separator || ',';
        thousands_separator = thousands_separator || '.';
        prefix = prefix || "";
        suffix = suffix || "";

        var str = this.toFixed(decimals).toString().split('.');
        var parts = [];
        for ( var i=str[0].length; i>0; i-=3 ) {
            parts.unshift(str[0].substring(Math.max(0,i-3),i));
        }
        str[0] = parts.join(thousands_separator);
        return prefix + str.join(decimal_separator) + suffix;
    };
}

if (!Number.prototype.money) {
    Number.prototype.money = function() {
        return this.format(2, ',', '.', '€ ');
    };
}