type-is

Infer the content-type of a request.

Install

This is a Node.js module available through the npm registry. Installation is done using the npm install command:

$ npm install type-is

API

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

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

typeis(request, 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'

typeis(req, ['json']) // => 'json'
typeis(req, ['html', 'json']) // => 'json'
typeis(req, ['application/*']) // => 'application/json'
typeis(req, ['application/json']) // => 'application/json'

typeis(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

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(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
  }
})