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Headers

expressly simplifies header manipulation on Request and Response objects.

🚨 Unlike Express, both req.headers and res.headers implement the standard Headers interface of the Fetch API.

Get header values​

Use *.headers.get(name) to retrieve the values of a HTTP header.

💡 Header names are case-insensitive!

router.get("/", (req, res) => {
  res.json({
    userAgent: req.headers.get("user-agent"),
    host: req.headers.get("host"),
  });
});

The .headers.entries() method returns an iterator for all header key/value pairs.

// List all header names and values.
for (const [name, value] of req.headers.entries()) {
  console.log(`${name}: ${value}`);
}

If you need only the keys or values, use *.headers.keys() or *.headers.values(), respectively.

Check if set​

If you need to check whether a header is set, use *.headers.has(name):

router.use((req, res) => {
  if (!req.headers.has("x-api-key")) {
    res.sendStatus(403);
  }
});

Set headers​

Set request or response headers by calling *.headers.set(key, value).

router.get("/", (req, res) => {
  res.headers.set("content-type", "text/html");
  res.send("<html><body><h1>This is HTML!</h1></body></html>");
});

Append headers​

Append to request or response headers by calling *.headers.append(key, value).

router.get("/", (req, res) => {
  res.headers.append("set-cookie", "auth=token");
  res.headers.append("set-cookie", "user=me");
  res.send("Hello world!");
});

Remove headers​

Remove request or response headers by calling *.headers.delete(key).

router.get("/", (req, res) => {
  req.headers.delete("x-api-key");
  // ...
});

Aliases​

req/res.set​

Aliased helpers to set HTTP header values. To set multiple fields at once, pass an object as the only parameter.

res.set("content-type", "text/plain");

req.set({
  "x-api-key": "my-api-key",
  "x-debug": "1",
  "host": "example.com"
});

req/res.append​

Aliased helpers to append HTTP header values. To set multiple fields at once, pass an object as the only parameter. To append iteratively to a single header, pass an array of strings as its value.

res.append("link", ["<http://localhost/>", "<http://localhost:3000/>"]);

req.append({
  "warning": "199 Miscellaneous warning",
  "x-forwarded-for": "example.com"
});