accepts

Higher level content negotiation for Deno using negotiator. Based on https://github.com/jshttp/accepts.

In addition to negotiator, it allows:

• Allows type shorthands such as json.
• Returns false when no types match
• Treats non-existent headers as *

API

import { Accepts } from "https://deno.land/x/accepts/mod.ts";

Accepts(headers: Headers)

Create a new Accepts object for the given header.

const accept = new Accepts(header);

accept.charsets(charsets?: string[]): string[] | string | boolean

Return the first accepted charset. If nothing in charsets is accepted, then false is returned.

Return the charsets that the request accepts, in the order of the client's preference (most preferred first).

accept.encodings(encodings?: string[]): string[] | string | boolean

Return the first accepted encoding. If nothing in encodings is accepted, then false is returned.

Return the encodings that the request accepts, in the order of the client's preference (most preferred first).

accept.languages(languages?: string[]): string[] | string | boolean

Return the first accepted language. If nothing in languages is accepted, then false is returned.

Return the languages that the request accepts, in the order of the client's preference (most preferred first).

accept.types(types?: string[]): string[] | string | boolean

Return the first accepted type (and it is returned as the same text as what appears in the types array). If nothing in types is accepted, then false is returned.

The types array can contain full MIME types or file extensions. Any value that is not a full MIME types is passed to mime_types's.lookup`.

Return the types that the request accepts, in the order of the client's preference (most preferred first).

Examples

Simple type negotiation

This simple example shows how to use accepts to return a different typed respond body based on what the client wants to accept. The server lists it's preferences in order and will get back the best match between the client and server.

import {
  serve,
  Response,
} from "https://deno.land/std@0.69.0/http/server.ts";
import { Accepts } from "../mod.ts";

const server = serve("127.0.0.1:3000");
console.log("Server listening on: 3000");

for await (const req of server) {
  const accept = new Accepts(req.headers);
  const res: Response = {
    headers: new Headers(),
  };
  let type = accept.types(["json", "html"]);
  if (type) {
    type = typeof type === "string" ? type : type[0];
    switch (type) {
      case "json":
        res.body = '{"hello":"world!"}';
        res.headers!.set("Content-Type", "application/json");
        break;
      case "html":
        res.body = "<b>hello, world!</b>";
        res.headers!.set("Content-Type", "text/html");
        break;
    }
  } else {
    // the fallback is text/plain, so no need to specify it above
    res.body = "hello, world!";
    res.headers!.set("Content-Type", "text/plain");
  }
  req.respond(res).catch(() => {});
}

You can test this out with the cURL program:

curl -I -H'Accept: text/html' http://localhost:3000/

License

MIT