type-is

What is type-is?

The type-is npm package is used to determine the MIME type of the content represented by a request or response object. It can check if the content type matches any of the given MIME types, which can be useful for handling requests in web applications, especially when dealing with REST APIs or any other HTTP-based interfaces.

What are type-is's main functionalities?

Check content type

This feature allows you to check if a given content type matches one of the specified MIME types. In the code sample, it checks if 'image/png' is an image MIME type.

const typeis = require('type-is');
const contentType = 'image/png';
const result = typeis.is(contentType, ['image/*']); // returns 'image/png'

Determine if request has body

This feature checks if the request object has a body by inspecting the 'Content-Type' header.

const typeis = require('type-is');
const req = { headers: { 'content-type': 'text/html' } };
const hasBody = typeis.hasBody(req); // returns true

Determine the type of request

This feature determines the type of the request by checking if the 'Content-Type' header matches any of the provided MIME types.

const typeis = require('type-is');
const req = { headers: { 'content-type': 'application/json' } };
const result = typeis(req, ['json', 'urlencoded', 'multipart']); // returns 'json'

Other packages similar to type-is

mime-types

The mime-types package is similar to type-is in that it provides functionality for looking up MIME types based on file extensions and vice versa. However, it does not directly deal with request objects and is more focused on the mapping between MIME types and file extensions.

content-type

The content-type package is used to parse and format 'Content-Type' headers. Unlike type-is, it does not provide methods to check if a request or response matches a specific content type, but it can be used to construct and deconstruct 'Content-Type' headers.

accepts

The accepts package is designed to deal with the HTTP Accept header, allowing servers to negotiate content type with clients. It is similar to type-is in that it helps determine the type of content, but it focuses on what the client can accept, rather than what the server is receiving or sending.

README

type-is

Infer the content-type of a request.

Install

$ npm install type-is

API

var http = require('http')
var is   = require('type-is')

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

type = is(request, types)

request is the node HTTP request. types is an array of types.

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

is(req, ['json'])             // 'json'
is(req, ['html', 'json'])     // 'json'
is(req, ['application/*'])    // 'application/json'
is(req, ['application/json']) // 'application/json'

is(req, ['html']) // false

is.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 existance works. If a body does exist, then this indicates that there is data to read from the Node.js request stream.

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

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

type = is.is(mediaType, types)

mediaType is the media type string. types is an array of types.

var mediaType = 'application/json'

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

is.is(mediaType, ['html']) // false

Each type can be:

• An 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.

false will be returned if no type matches or the content type is invalid.

null will be returned if the request does not have a body.

Examples

Example body parser

var is = require('type-is');

function bodyParser(req, res, next) {
  if (!is.hasBody(req)) {
    return next()
  }

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

License

MIT