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Response

The response object is the primary way to send data back to the client. expressly provides methods to set the response status, headers, and body.

res.send()​

The easiest way to deliver a response is to use the res.send() method. This method takes a single argument, which is the response body. The response body can be:

  • A string,
router.get('/', (req, res) => {
  res.send('Hello World!');
});
  • A ReadableStream,
router.get("/api", async (req, res) => {
  let originRequest = await fetch(
    "https://example.com", { backend: "my-origin" }
  );

  res.send(res.body);
});
  • Or a Response:
router.get("/origin", async (req, res) => {
  res.send(await fetch(
    "https://example.com", { backend: "my-origin" }
  ));
});

💡 If the experimental autoContentType configuration option is enabled, res.send will try to infer the Content-Type header from the data it is passed, if the header is not set.

res.end()​

Use to quickly end the response without any data. If you need to respond with data, instead use methods such as res.send() or res.json().

router.get('/', (req, res) => {
  res.end();
});

res.sendStatus()​

Sets the response HTTP status code to statusCode and sends the registered status message as the text response body.

router.get('/', (req, res) => {
  res.sendStatus(403); // "Forbidden"
});

res.redirect()​

When you want to redirect the user to another page, you can use the res.redirect() method. It will set a redirect status code and set the Location header to the URL you want to redirect to.

router.get('/', function(req, res) {
  res.redirect('/about');
});

💡 This method accepts a second, optional argument – the redirect status code (defaults to 302).

router.get("/redirect", async (req, res) => {
  res.redirect("https://fastly.com", 307);
});

res.json()​

To return a serialized JSON response (Content-Type: application/json):

router.get('/', function(req, res) {
  res.json({
    message: 'Hello world!'
  });
});

res.text()​

To return a plain-text response (Content-Type: text/plain):

router.get("/api", async (req, res) => {
  res.text("Hello world!");
});

res.html()​

To return a HTML response (Content-Type: text/html[; charset=my-charset]):

router.get("/page", async (req, res) => {
  // Takes a second, optional argument specifying a charset:
  res.html("<html><body><h1>This is HTML!</h1></body></html>", "utf-8");
});

res.withStatus()​

expressly provides a chainable method to set the status code of a response:

router.get("/page", async (req, res) => {
  res
    .withStatus(404)
    .html("<html><body><h1>Page not found</h1></body></html>");
});

res.on('finish', callback)​

Provides a useful listener for tidying up any post-request actions (e.g., sending logs, metrics or traces).

Note: The finish event is emitted immediately before the final response headers and body are handed off to the Fastly Compute platform, to send back to the client.

router.use((_, res) => {
  res.on("finish", (finalResponse) => {
    console.log("Response sent!", finalResponse);
  });
});

Response headers​

Read more about manipulating response (and request) headers with expressly.

Cookies​

Read how to set and expire response cookies.

Cache segmentation​

res.vary()​

Appends a field to the Vary response header.

res.vary("x-feature-flags");

res.surrogateKeys​

expressly exposes res.surrogateKeys, a Set object that allows you to manipulate the Surrogate-Key header.

res.surrogateKeys.add("seasonal");
res.surrogateKeys.add("vegan");
res.surrogateKeys.delete("low-carb");

// List all surrogate keys
for (const key of res.surrogateKeys) {
  console.log(key);
}