type-is

Infer the content-type of a request.

Install

$ npm install type-is

API

import { createServer } from "http";
import * as typeis from "type-is";

http.createServer(function (req, res) {
  var istext = typeis.request(req, ["text/*"]);
  res.end("you " + (istext ? "sent" : "did not send") + " me text");
});

request(req, types)

Checks if the request is one of the types. If the 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 request argument is expected to be a Node.js HTTP request. 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:

// req.headers.content-type = 'application/json'

request(req, ["json"]); // => 'json'
request(req, ["html", "json"]); // => 'json'
request(req, ["application/*"]); // => 'application/json'
request(req, ["application/json"]); // => 'application/json'

request(req, ["html"]); // => false

typeis.hasBody(request)

Returns a Boolean if the given 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 Node.js request stream.

if (typeis.hasBody(req)) {
  // read the body, since there is one

  req.on("data", function (chunk) {
    // ...
  });
}

typeis.is(mediaType, types)

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:

var mediaType = "application/json";

typeis.is(mediaType, ["json"]); // => 'json'
typeis.is(mediaType, ["html", "json"]); // => 'json'
typeis.is(mediaType, ["application/*"]); // => 'application/json'
typeis.is(mediaType, ["application/json"]); // => 'application/json'

typeis.is(mediaType, ["html"]); // => false

typeis.match(expected, actual)

Match the type string expected with actual, taking in to account wildcards. A wildcard can only be in the type of the subtype part of a media type and only in the expected value (as actual should be the real media type to match). A suffix can still be included even with a wildcard subtype. If an input is malformed, false will be returned.

typeis.match("text/html", "text/html"); // => true
typeis.match("*/html", "text/html"); // => true
typeis.match("text/*", "text/html"); // => true
typeis.match("*/*", "text/html"); // => true
typeis.match("*/*+json", "application/x-custom+json"); // => true

typeis.normalize(type)

Normalize a type string. This works by performing the following:

• If the type is not a string, false is returned.
• If the string starts with + (so it is a +suffix shorthand like +json), then it is expanded to contain the complete wildcard notation of */*+suffix.
• If the string contains a /, then it is returned as the type.
• Else the string is assumed to be a file extension and the mapped media type is returned, or false is there is no mapping.

This includes two special mappings:

• 'multipart' -> 'multipart/*'
• 'urlencoded' -> 'application/x-www-form-urlencoded'

Examples

Example body parser

var express = require("express");
var typeis = require("type-is");

var app = express();

app.use(function bodyParser(req, res, next) {
  if (!typeis.hasBody(req)) {
    return next();
  }

  switch (typeis.request(req, ["urlencoded", "json", "multipart"])) {
    case "urlencoded":
      // parse urlencoded body
      throw new Error("implement urlencoded body parsing");
    case "json":
      // parse json body
      throw new Error("implement json body parsing");
    case "multipart":
      // parse multipart body
      throw new Error("implement multipart body parsing");
    default:
      // 415 error code
      res.statusCode = 415;
      res.end();
      break;
  }
});

License

MIT