Using Stream PassThrough to pass same output buffer to multiple destination

passthrough-example.js

const PDFMake = require("pdfmake");
const AWS = require("aws-sdk");
const nodemailer = require("nodemailer");
const { PassThrough } = require("stream");

//aws: update your AWS credentials
const accessKeyId = "{aws_accesskey}";
const secretAccessKey = "{aws_secret}";
const region = "us-east-1";

//pdfmake: make sure you have Roboto fonts in this path
const fonts = {
  Roboto: {
    normal: __dirname + "/resources/fonts/Roboto-Regular.ttf",
    bold: __dirname + "/resources/fonts/Roboto-Medium.ttf",
    italics: __dirname + "/resources/fonts/Roboto-Italic.ttf",
    bolditalics: __dirname + "/resources/fonts/Roboto-MediumItalic.ttf"
  }
};

//pdfmake: sample document definition to create a document
const documentDefinition = {
  pageSize: "A4",
  pageOrientation: "landscape",
  pageMargins: [0, 0, 0, 0],
  content: [
    {
      text: "Great PDF",
      alignment: "center",
      fontSize: 45,
      absolutePosition: { x: 0, y: 255 }
    },
    {
      text: `Thank you for creating this PDF`,
      bold: true,
      alignment: "center",
      color: "#A91F24",
      fontSize: 12,
      absolutePosition: { x: 0, y: 340 }
    }
  ]
};

const MakePDFUploadAndEmail = () => {
  const printer = new PDFMake(fonts);
  const pdfDoc = printer.createPdfKitDocument(documentDefinition);

  //notice pdfDoc buffer is piped twice here
  pdfDoc.pipe(awsUpload());
  pdfDoc.pipe(sendEmail());

  pdfDoc.end();
};

const awsUpload = data => {
  console.log("---Processing AWS");
  const s3 = new AWS.S3({ apiVersion: "2006-03-01", accessKeyId, secretAccessKey, region });

  //captured the piped buffer here
  const doc = new PassThrough();

  var params = {
    Bucket: "my-bucket",
    Key: `test/test.pdf`,
    ACL: "public-read",
    ContentType: "application/pdf",
    Body: doc
  };

  s3.upload(params, function(err, data) {
    if (err) console.log(err);
    console.log(data);
  });

  return doc;
};

const sendEmail = data => {
  console.log("---Processing Email");
  //captured the piped buffer here
  const doc = new PassThrough();

  var ses = new AWS.SES({ accessKeyId, secretAccessKey, region });
  var transporter = nodemailer.createTransport({
    SES: ses
  });

  var params = {
    from: "mySESregistedEmail@gmail.com",
    to: "passthroughtest@mailinator.com",
    subject: "This is subject",
    html: "Here is the attachment",
    attachments: [
      {
        filename: "attachment.pdf",
        content: doc
      }
    ]
  };

  transporter.sendMail(params, function(err, data) {
    if (err) console.log(err);
    console.log(data);
  });

  return doc;
};

//run the code using "node ./passthrough-example.js"
MakePDFUploadAndEmail();