type_is

Infer the content-type of a HTTP Header for Deno, compatible with Browser. Based on https://github.com/jshttp/type-is.

API

import { is, typeofrequest, hasBody } from "https://deno.land/x/type_is/mod.ts";

is(mediaType: string, types?: string[]): boolean | string

Checks if the mediaType is one of the types. If the mediaType is invalid or does not matches any of the types, then false is returned. Otherwise, a string of the type that matched is returned.

The mediaType argument is expected to be a media type string. The types argument is an array of type strings.

Each type in the types array can be one of the following:

• A file extension name such as json. This name will be returned if matched.
• A mime type such as application/json.
• A mime type with a wildcard such as */* or */json or application/*. The full mime type will be returned if matched.
• A suffix such as +json. This can be combined with a wildcard such as */vnd+json or application/*+json. The full mime type will be returned if matched.

Some examples to illustrate the inputs and returned value:

const mediaType = 'application/json'

is(mediaType, ['json']) // => 'json'
is(mediaType, ['html', 'json']) // => 'json'
is(mediaType, ['application/*']) // => 'application/json'
is(mediaType, ['application/json']) // => 'application/json'

is(mediaType, ['html']) // => false

typeofrequest(header: Headers, types?: string[]): null | boolean | string

Checks if the header is one of the types. If the header’s request has no body, even if there is a Content-Type header, then null is returned. If the Content-Type header is invalid or does not matches any of the types, then false is returned. Otherwise, a string of the type that matched is returned.

The header argument is expected to be a Deno’s Headers, it should be compatible with browser’s Headers as well. The types argument is an array of type strings.

Each type in the types array can be one of the following:

• A file extension name such as json. This name will be returned if matched.
• A mime type such as application/json.
• A mime type with a wildcard such as */* or */json or application/*. The full mime type will be returned if matched.
• A suffix such as +json. This can be combined with a wildcard such as */vnd+json or application/*+json. The full mime type will be returned if matched.

Some examples to illustrate the inputs and returned value:

const header = new Headers([["content-type", "application/json"]]);

typeis(header, ["json"]) // => "json"
typeis(header, ["html", "json"]) // => "json"
typeis(header, ["application/*"]) // => "application/json"
typeis(header, ["application/json"]) // => "application/json"
typeis(header, ["html"]) // => false

Example in Deno http server:

import {
  serve
} from "https://deno.land/std/http/server.ts";
import { typeofrequest } from "https://raw.githubusercontent.com/ako-deno/type_is/master/mod.ts";

const server = serve("127.0.0.1:4500");

for await (const req of server) {
  const isText = typeofrequest(req.headers, ['text/*'])
  const res = {
    body: `you ${istext ? 'sent' : 'did not send'} me text`,
    headers: new Headers(),
  };
  req.respond(res).catch(() => {});
}

hasBody(header: Headers): boolean

Returns a Boolean if the given header’s request has a body, regardless of the Content-Type header.

Having a body has no relation to how large the body is (it may be 0 bytes). This is similar to how file existence works. If a body does exist, then this indicates that there is data to read from the Deno’s request stream.

License

MIT