Convert JSON object to Lua (string)

JSON.toLua = function (obj) {
    if (obj === null || obj === undefined) {
        return "nil";
    }
    if (!_.isObject(obj)) {
        if (typeof obj === 'string') {
            return '"' + obj + '"';
        }
        return obj.toString();
    }
    var result = "{";
    var isArray = obj instanceof Array;
    var len = _.size(obj);
    var i = 0;
    _.forEach(obj, function (v, k) {
        if (isArray) {
            result += JSON.toLua(v);
        } else {
            result += '["' + k + '"] = ' + JSON.toLua(v);
        }
        if (i < len-1) {
            result += ",";
        }
        ++i;
    });
    result += "}";
    return result;
};

JSON.toLua([42, null, [77, 45], "test", true, {a:66, "$b": 99}]);

JSON.toLua([
  {"deltaX":23,"deltaY":21,"x":256,"y":722,"altKey":false,"ctrlKey":false,"shiftKey":false,"inputType":5}, 
  {"deltaX":19,"deltaY":15,"x":275,"y":707,"altKey":false,"ctrlKey":false,"shiftKey":false,"inputType":5}
]);