NodeJS从mongo添加数字

Question

我在快递中有这个基本代码

var currpoints = user.points;
var addedpoints = req.body.points;
var newpoints = currpoints+addedpoints;

user.points = newpoints;

如果currentpoints = 10和addedpoints = 100则为var newpoints返回10100。

如何改变这一点，以便增加10 + 100到110？