How to send emails to the registered users automatically by different dates-CodePudding

I am doing a MERN Stack project. In my collection on MongoDB. a single document contains feilds like

userName
email
lastDate

The lastDate property is different for different users. I want to send an email to every user before 3 days of the lastDate automatically. I have no idea how to do that. Please give me guidelines on how to do that. Thank you!

CodePudding user response：

Well, In the past I was looking for a similar solution, I found this, you can use the module named node-cron with nodemailer.

First install it.

node install node-cron --save

Import node-cron and schedule a task

let cron = require('node-cron');

cron.schedule('* * * * *', () => {
   console.log('running a task every minute');
});

Note: You can read about several cron schedule patterns here. In the above example, we have scheduled a simple console log in every minute.

Here is the combined code where I am scheduling the e-mail to send every minute:

  let cron = require('node-cron');
  let nodemailer = require('nodemailer');

  // e-mail message options
  let mailOptions = {
        from: '<FROM_EMAIL_ADDRESS>',
        to: '<TO_EMAIL_ADDRESS>',
        subject: 'Email from Node-App: A Test Message!',
        text: 'Some content to send'
   };

  // e-mail transport configuration
  let transporter = nodemailer.createTransport({
        service: 'gmail',
        auth: {
          user: '<FROM_EMAIL_ADDRESS>',
          pass: '<FROM_EMAIL_PASSWORD>'
        }
    });

 cron.schedule('* * * * *', () => {
  // Send e-mail
  transporter.sendMail(mailOptions, function(error, info){
        if (error) {
          console.log(error);
        } else {
          console.log('Email sent: '   info.response);
        }
    });
  });