Question

我是nodejs和mongoose的新手。我有一个从2009年到现在的数据库，想要计算每个月的数据，并返回为json数组。慢速异步回调导致所有日期为2014年8月1日

实现这个的正确方法是什么？

var dbURL = 'mongodb://localhost/database';
var db = require('mongoose').connect(dbURL);
var c_db = require('./models/models.js').c_db;

var start_date = new Date(2009,0,1);
end_date = new Date(2014,8,1),
next_date = new Date();

var test_json=[];

var total_months = (end_date.getFullYear() - start_date.getFullYear())*12 + (end_date.getMonth() - start_date.getMonth());

var next_date = start_date;

for(var i=0;i<total_months;i++){

  var firstDay = new Date(next_date.getFullYear(), next_date.getMonth(), 1);
  var lastDay = new Date(next_date.getFullYear(), next_date.getMonth() + 1, 0);
  next_date.setDate(lastDay.getDate()+1);

  c_db.count({'shipdate':{'$gte':new Date(firstDay),'$lte':new Date(lastDay)}},function(err,query){

    var item = {
      "Date": firstDay,
      "Count": query
    }
    test_json.push(item);
  });

}

setTimeout(function(){
  console.log(test_json);
},5000);

Answer 1

使用异步回调编写javascript时要小心。您要做的是在当前异步完成时继续循环中的下一个项目。您可以使用＆＃34; async＆＃34;模块：https://github.com/caolan/async

var async = require("async");
var dbURL = 'mongodb://localhost/database';
var db = require('mongoose').connect(dbURL);
var c_db = require('./models/models.js').c_db;

var start_date = new Date(2009,0,1);
end_date = new Date(2014,8,1),
next_date = new Date();

var test_json=[];

var total_months = (end_date.getFullYear() - start_date.getFullYear())*12 + (end_date.getMonth() - start_date.getMonth());

var next_date = start_date;

async.timesSeries(total_months, function(n, next) {
  var firstDay = new Date(next_date.getFullYear(), next_date.getMonth(), 1);
  var lastDay = new Date(next_date.getFullYear(), next_date.getMonth() + 1, 0);
  next_date.setDate(lastDay.getDate()+1);

  c_db.count({'shipdate':{'$gte':new Date(firstDay),'$lte':new Date(lastDay)}},function(err,query){

    var item = {
      "Date": firstDay,
      "Count": query
    }
    test_json.push(item);
    next();
  });
}, function(e) {
  console.log(test_json);
});

使用nodejs异步回调处理循环

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