string.format in Javascript

String.prototype.format = function format()
{
    if (arguments.length == 0) return this;

    var data;
    if (arguments.length > 1) data = arguments;
    else if (typeof arguments[0] == 'object') data = arguments[0];
    else data = arguments;

    return this.split('{{').map(function (q)
    {
        return q.replace(/\{([^\{\}]+)\}/g, function ($0, $1)
        {
            return data[$1];
        });
    }).join('{').replace(/\}\}/g, '}');
};