AbortController in Express.js

app.js

const express = require("express");

const app = express();

console.log("initializing")

app.get("/foo", (req, res) => {
  const abort = new AbortController()

  console.log("entered /foo")

  req.on('end', () => {
    // this is only called when the request successfully sent a response
    console.log("ended");
  });
  req.on('close', () => {
    // this is called everytime the request ends - no matter
    // whether a response was sent successfully or not
    abort.abort();
    console.log("closed");
  });

  const timeout = setTimeout(() => {
    console.log("Completed")
    res.sendStatus(200);
  }, 2000);

  abort.signal.onabort = () => {
    // this clears the timeout, so if the client cancels the request within
    // the 2 seconds of `setTimeout`, `Completed` will not be printed
    console.log("aborted")
    clearTimeout(timeout);
  };
});

app.listen(3000)

Usage: $ node express-abort.js

Sequence of log output:

initializing

# successful request
entered /foo
Completed
ended
aborted
closed

# request cancelled by client
entered /foo
aborted
closed