ETag

npm i @inkanjs/etag

import { etag } from "@inkanjs/etag";

app
  .register(etag())
  .register(compress()) // in any order: compress always runs after etag
  .get("/teas", () => listTeas());

GET /teas                                → 200, etag: "kq3T…"
GET /teas  if-none-match: "kq3T…"        → 304, no body

A client that already has an answer gets an empty 304 instead of the same body again. The tag is a hash of exactly the bytes that are sent.

BehaviourCopy Anchor Link

• Which answers. 2xx answers (not 204 or 206) to GET and HEAD whose body is whole: JSON, text, a buffer. Streams, server-sent events and rows written one by one are left alone, since their bytes are not known before they go out.
• Which bytes. SHA-1, base64url, of the body as the client gets it: JSON as the contract wrote it, text as UTF-8. compress runs after every other onSend hook (order: "last"), so the tag is that of the unpacked body, the same for gzip, brotli and none.
• If-None-Match. A list, *, and W/ tags, compared weakly as RFC 9110 asks: W/"a" matches "a". A match is a 304 with the tag and the other headers, without content-type, content-length and the body.
• Your own tag. An etag the handler set (a version number, an updated_at) is kept and compared instead of hashing the body.
• The handler still runs for a 304: the tag is of its answer. To save the work as well, compare a tag of your own (a row version) in the handler.
• If-Modified-Since, If-Match and ranges are not handled.

OptionsCopy Anchor Link

etagOf(body, weak?) and noneMatch(header, tag) are exported too.

OpenAPICopy Anchor Link

Unchanged. It is a shared plugin: registered on the app it serves every route, inside a plugin only that plugin's routes.