@httpland/http-etag

http-etag

ETag middleware for standard Request and Response.

Middleware

For a definition of Universal HTTP middleware, see the http-middleware project.

Usage

Middleware is exported by default.

Add etag field to HTTP Response header. Or, check the etag and return the appropriate 304 HTTP response.

The ETag is computed from a hash of the Response body.

By default, the SHA-1 algorithm of the Web Crypto API is used. This is because it requires no additional code and is faster.

Calculate ETag:

import etag from "https://deno.land/x/http_etag@$VERSION/mod.ts";
import { assertEquals } from "https://deno.land/std/testing/asserts.ts";

const middleware = etag();
const response = await middleware(
  new Request("http://localhost"),
  (request) => new Response("ok"),
);

assertEquals(response.headers.get("etag"), "<body:SHA-1>");

Check ETag:

import etag from "https://deno.land/x/http_etag@$VERSION/mod.ts";
import { assert, assertEquals } from "https://deno.land/std/testing/asserts.ts";

const middleware = etag();
const response = await middleware(
  new Request("http://localhost", { headers: { "if-none-match": "<etag>" } }),
  (request) => new Response("ok", { headers: { "x-server": "deno" } }),
);

assertEquals(response.status, 304);
assertEquals(await response.text(), "");
assert(response.headers.has("x-server"));

Customize hash algorithm

You can change the hash algorithm from the digest filed.

import etag from "https://deno.land/x/http_etag@$VERSION/mod.ts";
import { assertEquals } from "https://deno.land/std/testing/asserts.ts";

const middleware = etag({
  digest: (data) => crypto.subtle.digest("sha-256", data),
});
const response = await middleware(
  new Request("http://localhost"),
  (request) => new Response("ok"),
);

assertEquals(response.headers.get("etag"), "<body:SHA-256>");

The digest function must satisfy the following interfaces:

License

Copyright © 2023-present httpland.

Released under the MIT license