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.
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.
is(req, ['json'])
is(req, ['html', 'json'])
is(req, ['application/*'])
is(req, ['application/json'])
is(req, ['html'])
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'])
is.is(mediaType, ['html', 'json'])
is.is(mediaType, ['application/*'])
is.is(mediaType, ['application/json'])
is.is(mediaType, ['html'])
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
*/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.
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':
throw new Error('implement urlencoded body parsing')
break
case 'json':
throw new Error('implement json body parsing')
break
case 'multipart':
throw new Error('implement multipart body parsing')
break
default:
res.statusCode = 415
res.end()
return
}
}
License
MIT