Node JS Promises 然后链接不按顺序

Question

我正在尝试让我的 Node JS 代码逐步工作，而不是使用 Promise 进行异步操作。

我首先删除所有电子表格，然后生成它们，然后压缩它们，然后加密 zip，然后通过电子邮件发送 zip，然后删除电子表格。

//Schedules the job at a specific time
var start = schedule.scheduleJob({
  hour: 19,
  minute: 26,
  dayOfWeek: 3
}, function() {
  sendIt();
});

//Starts the Promise Chain
function sendIt() {
  return deleteSpreadsheets().then(generateSpeadsheets).then(zipSpreadsheets).then(encrypt).then(sendEmail).then(deleteSpreadsheets);
}

//Deletes the current Spreadsheets in the folder
function deleteSpreadsheets() {
  var promise = new Promise(function(resolve, reject) {
    console.log('Deleting Spreadsheets');
    var locationSpread = ['Location.xlsx'];

    locationSpread.forEach(function(filename) {

      if (fs.existsSync("./Spreadsheets/" + filename)) {
        fs.unlink("./Spreadsheets/" + filename, (err) => {
          if (err) {
            console.log('Spreadsheet ' + filename + ' not found');
          } else {
            console.log('Spreadsheet ' + filename + ' successfully deleted');
          }
        });
      }
    });
    resolve();
  });
  return promise;
}

//Generates the new Spreadsheets
function generateSpeadsheets() {

  var promise = new Promise(function(resolve, reject) {
    console.log('Generating Spreadsheets');

    var locationSpread = ['Location.xlsx'];

    locationSpread.forEach(function(filename) {

      var query = connection.query('SELECT * from ' + filename.slice(0, -5), function(err, rows) {

        var workbook = excelbuilder.createWorkbook('./Spreadsheets/', filename);
        if (workbook == null) {
          console.log('workbook null')
        };

        var sheet = workbook.createSheet(filename.slice(0, -5), 3, rows.length + 1);
        if (sheet == null) {
          console.log('sheet null')
        };
        sheet.set(1, 1, 'First Name');
        sheet.set(2, 1, 'Last Name');
        sheet.set(3, 1, 'Company');

        for (var j = 2, z = 0; z < rows.length; j++, z++) {
          sheet.set(1, j, rows[z].firstName);
          sheet.set(2, j, rows[z].lastName);
          sheet.set(3, j, rows[z].company);
        }

        workbook.save(function(err) {
          console.log('workbook saved ' + (err ? 'failed' : 'ok'));
        });
      });
    });
    resolve();
  });
  return promise;
}

//Generates a Zip file with all the Spreadsheets
function zipSpreadsheets() {

  var promise = new Promise(function(resolve, reject) {
    console.log('Zipping Spreadsheets');
    var zipFolder = require('zip-folder');
    zipFolder('./Spreadsheets/', './Spreadsheets.zip', function(err) {
      if (err) {
        console.log('Failed to zip folders', err);
        reject();
      } else {
        console.log('Successfully zipped folder');
      }
    });
    resolve();
  });
  return promise;
}

//Encrypts the Spreadsheet
function encrypt() {

  var promise = new Promise(function(resolve, reject) {
    console.log('Encrypting');
    spawn = require('child_process').spawn;
    zip = spawn('zip', ['-P', 'something', 'Encrypted.zip', './Spreadsheets.zip']);
    zip.on('exit', function(code) {
      console.log('Finished encrypting');
      resolve();
    });
  });

  return promise;
}

//Sends the Encryped Zip as an attached in an email
function sendEmail() {

  var promise = new Promise(function(resolve, reject) {
    console.log("MAIL SCHEDULE RUNNING");

    var transporter = nodemailer.createTransport({
      service: 'Gmail',
      auth: {
        user: 'email', // Your email id
        pass: 'password'
      }
    });

    var content = 'something';

    var mailOptions = {
      from: 'email', // sender address
      to: 'email', // list of receivers
      subject: 'Title', // Subject line
      text: content,
      attachments: [{
        // file on disk as an attachment
        filename: 'Encrypted.zip',
        path: './Encrypted.zip' // stream this file
      }]
    };

    transporter.sendMail(mailOptions, function(error, info) {
      if (error) {
        console.log(error);
        reject();
      } else {
        console.log('Message sent: ' + info.response);
        resolve();
      };
    });
  });
  return promise;
}

这似乎不像日志中看到的那样按计划工作：

Deleting Spreadsheets  
Generating Spreadsheets 
Zipping Spreadsheets   
Encrypting            
**Spreadsheet Location.xlsx successfully deleted**
**Finished encrypting**    
MAIL SCHEDULE RUNNING
**Successfully zipped folder**
**workbook saved ok**
Message sent: -----------------------------------------------
Deleting Spreadsheets
Spreadsheet Location.xlsx successfully deleted

应该是这样的：

Deleting Spreadsheets  
**Spreadsheet Location.xlsx successfully deleted**
Generating Spreadsheets 
**workbook saved ok**
Zipping Spreadsheets   
**Successfully zipped folder**
Encrypting            
**Finished encrypting**    
MAIL SCHEDULE RUNNING
Message sent: -----------------------------------------------
Deleting Spreadsheets
Spreadsheet Location.xlsx successfully deleted

Answer 1

您正在返回承诺，然后以错误的方式解决。此外，您不会等待所有删除发生。看看这个。

function deleteSingle(filename) {
  return new Promise((resolve, reject) => {
    if (fs.existsSync("./Spreadsheets/" + filename)) {
      fs.unlink("./Spreadsheets/" + filename, (err) => {
        //handle errors or whatever
        return resolve();  
      });
    } else {
      //handle if file doesnt exist
      return resolve();
    }
  })
}

//Deletes the current Spreadsheets in the folder
function deleteSpreadsheets() {
  //we are maping each value inside locationSpread and passing it to the deleteSingle function which returns a promise
  return Promise.all(locationSpread.map(deleteSingle))
}

所以，我拆分了您的代码。 deleteSingle 函数返回一个承诺，一旦文件被删除，它就会解决（如果文件没有被删除或不存在，它也会解决，你可以修改它来做任何你想做的事情）。

然后，deleteSpreadsheets 函数返回一个单一的 Promise，一旦内部的 Promise 数组解析，它就会被解析。所以你可以打电话给deleteSpreadsheets().then....等