NodeJS承诺等待foreach循环的完成

Question

我有一个NodeJS脚本，它为用户调用API，为每个用户获取多个数据并将其全部写入本地文件。一旦所有的数据都写入到文件中，我将尝试将该文件上传到服务器。问题是，在文件完全填充之前，应该上载文件的代码就会被执行。代码写在下面。我不知道如何做出承诺，等待第一个功能完成。

var fs = require('fs');
var server = require('some-server');
var service = require('./some-service.js');
var moment = require('moment-timezone');
var csvWriter = require('csv-write-stream');
var writer = csvWriter({
sendHeaders: false
});

var users = require('./some-users')
writer.pipe(fs.createWriteStream('myFile' + '.txt'))

service.login().then(function (response) {

users.forEach(function (user) {

    service.getSpecificUser(user).then(function (response) {

        var myUser = JSON.parse(response)
        service.getDataForUser(user.Info).then(function (response) {
            var userData = JSON.parse(response);
            if (userData.IsValid) {
                userData.AdditionalInfo.forEach(function (additionalInfo) {
                    service.getAdditionalInfo(myUser.Info, userData.data).then(function (response) {

                        //Collect additional info and combine final results to write into file
                        // write to output csv file
                        writer.write({
                            //write information that is of interest
                        })

                    }, function (error) {
                        console.log('error getting additional data', error);
                    })
                }
                )
            }
        }, function (error) {
            console.log('error getting user data', error)
        })
    }, function (error) {
        console.log('error', myUser, error)
    })
});
}, function (error) {
 console.log('not logged', response);
}).then(function () {
//perform uploading to server
var fpath = 'path of file that contains downloaded data'
console.log("Trying to upload to file: " +fpath)
service.UploadFile(fpath, function (error, result, response) {
    if (!error) {
        console.log("Uploaded " + name);
    }
    else {
        console.log(error);
    }

})
})

任何帮助都将不胜感激。

Answer 1

你可以用Promise.all()，Array.prototytpe.map()代替.forEach()。csv-write-steam的文档似乎使用.end()来完成对.write()的最后.then()调用。

  service.login().then(function(response) {
    return Promise.all(users.map(function(user) {
      return service.getSpecificUser(user).then(function(response) {
        var myUser = JSON.parse(response)
        return service.getDataForUser(user.Info).then(function(response) {
          var userData = JSON.parse(response);
          if (userData.IsValid) {
            return Promise.all(userData.AdditionalInfo.map(function(additionalInfo) {
              return service.getAdditionalInfo(myUser.Info, userData.data).then(function(response) {
                //Collect additional info and combine final results to write into file
                // write to output csv file
                writer.write({
                  //write information that is of interest
                });
              })
            }))
          }
        })
      })
    }));
  })
  .then(function() {
   writer.end();
    //perform uploading to server
    var fpath = 'path of file that contains downloaded data'
    console.log("Trying to upload to file: " + fpath)
    service.UploadFile(fpath, function(error, result, response) {
      if (!error) {
        console.log("Uploaded " + name);
      } else {
        console.log(error);
      }

    })
  })
  .catch(function(e) {
    console.log(e)
  })