@httpland/compression-middleware NPM

compression-middleware

HTTP compression middleware.

Compresses HTTP Content(body).

Compliant with RFC 9110, 8.4. Content-Encoding and RFC 9110, 12.5.3. Accept-Encoding .

Middleware

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

Usage

Middleware convert message body and adds the Content-Encoding header to the response.

Also, safely add Accept-Encoding to the Vary header in response.

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

const middleware = compression();
const request = new Request("test:", {
  headers: {
    "accept-encoding": "deflate;q=0.5, gzip;q=1.0",
  },
});

const response = await middleware(
  request,
  () => new Response("<body>"),
);

assertEquals(await response.text(), "<gzip:body>");
assertEquals(response.headers.get("content-encoding"), "gzip");

yield:

Content-Encoding: <encoding>
Vary: accept-encoding

Built-in encoding

Middleware supports the following encodings by default:

gzip
deflate

Additional encoding

You can add supported encoding.

There are two ways to add encodings:

Encoding map
Encoder list

In either style, the result is the same.

When encoding is added, a shallow merge is performed in favor of user-defined.

Encoding map

Encoding map defines a map of encoding formats and encode functions .

Example of adding brotli encoding:

import {
  compression,
  type Encode,
  type EncodingMap,
} from "https://deno.land/x/compression_middleware@$VERSION/mod.ts";

declare const encodeBr: Encode;
const encodingMap: EncodingMap = { br: encodeBr };

const middleware = compression(encodingMap);

Encoder list

Encoder list defines a list of Encoder.

Encoder is a following structured object:

Name	Type	Description
encoding	`string`	Encoding format.
encode	Encode	Encode stream.

Example of adding brotli encoding:

import {
  compression,
  type Encode,
  type Encoder,
} from "https://deno.land/x/compression_middleware@$VERSION/mod.ts";

declare const encodeBr: Encode;
const Br: Encoder = { encoding: "br", encode: encodeBr };

const middleware = compression([Br]);

Encode API

Encode is an API for converting content.

interface Encode {
  (stream: ReadableStream<Uint8Array>): BodyInit | Promise<BodyInit>;
}

Compressible

Filter media types to be compressed according to the following specifications:

If the media type includes an inherent encoding, such as a data format that is always compressed, then that encoding would not be restated in Content-Encoding even if it happens to be the same algorithm as one of the content codings.

Determine from the Content-Type response header whether the representation is compressible.

For example, image media such as image/jpag is not compressible because it is already compressed.

Content-Length

If the Response has a Content-Length header, compression may cause the actual content length to deviate.

In that case, the Content-Length is recalculated.

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

declare const request: Request;
const middleware = compression();

const response = await middleware(
  request,
  () =>
    new Response("<body>", { headers: { "content-length": "<body:length>" } }),
);

assertEquals(await response.text(), "<gzip:body>");
assertEquals(response.headers.get("content-length"), "<gzip:body:length>");