To download files from a Node.js server to a client, you have to read the file and set the response header Content-Disposition.

Let's say we have a PDF named resume.pdf in a directory called docs and we want to download that PDF whenever the user goes to /resume endpoint.

Let's write the code for that. 🦄

First create a read stream to read the file like this,

// filesystem module
const fs = require("fs");

// endpoint for /resume
app.get("/resume", (req, res) => {
  const rs = fs.createReadStream("./docs/resume.pdf");
});

After that, set the Content-Disposition response header and give the value as attachment; filename=nameOftheFileYouWant.pdf. This tells the user's browser that this is an attachment that needs to download it.

// filesystem module
const fs = require("fs");

// endpoint for /resume
app.get("/resume", (req, res) => {
  // create read steam for the pdf
  const rs = fs.createReadStream("./docs/resume.pdf");

  // set response header: Content-Disposition
  res.setHeader("Content-Disposition", "attachment; john-resume.pdf");
});

After setting the header all you have to do is pipe the read stream to the Response object res using the pipe() method like his,

// filesystem module
const fs = require("fs");

// endpoint for /resume
app.get("/resume", (req, res) => {
  // create read steam for the pdf
  const rs = fs.createReadStream("./docs/resume.pdf");

  // set response header: Content-Disposition
  res.setHeader("Content-Disposition", "attachment; john-resume.pdf");

  // pipe the read stream to the Response object
  rs.pipe(res);
});

If you are using Express.js, you can use the res.download() method and pass the file path as the argument to it like this.

// filesystem module
const fs = require("fs");

// endpoint for /resume
app.get("/resume", (req, res) => {
  // express.js
  res.download("./docs/resume.pdf");
});

Feel free to share if you found this useful 😃.