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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
}
})

# License

[MIT](LICENSE)