从mongoDB中采样不能在循环中工作

Question

我的API中有一条路线。当您应用于此路由器时，将生成最近7天，并在一天中的每一天从数据库中提取元素。但显然是因为异步，样本不能正常运行。

apiRoutes.get('/costs/chart', function (req, res) {

    var currentDay = moment().format('L');
    var currentWeekDays = [];

    for (var i = 0; i < 7; i++) {
        var day = {
            date: (function () {
                var date = moment().add(-[i], 'd');
                return moment(date).format('L');
            })(),
            costs: []
        };

        Cost.find({formatDate: day.date}, function (err, costs) {
            if (costs.length > 0) {
                console.log(costs);
                day['costs'] = costs;
            }
        });

        currentWeekDays.push(day);
    }

    var result = {
        content: {
            currentDay: currentDay,
            currentWeekDays: currentWeekDays
        }
    };

    res.json(result);
});