cors
Node.js CORS middleware
cors
CORS is a node.js package for providing a Connect/Express middleware that can be used to enable CORS with various options.
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Installation
This is a Node.js module available through the
npm registry. Installation is done using the
npm install
command:
$ npm install cors
Usage
Simple Usage (Enable All CORS Requests)
var express = var cors = var app = app app app
Enable CORS for a Single Route
var express = var cors = var app = app app
Configuring CORS
var express = var cors = var app = var corsOptions = origin: 'http://example.com' optionsSuccessStatus: 200 // some legacy browsers (IE11, various SmartTVs) choke on 204 app app
Configuring CORS w/ Dynamic Origin
var express = var cors = var app = var whitelist = 'http://example1.com' 'http://example2.com'var corsOptions = { if whitelist !== -1 else } app app
If you do not want to block REST tools or server-to-server requests,
add a !origin
check in the origin function like so:
var corsOptions = { if whitelist !== -1 || !origin else }
Enabling CORS Pre-Flight
Certain CORS requests are considered 'complex' and require an initial
OPTIONS
request (called the "pre-flight request"). An example of a
'complex' CORS request is one that uses an HTTP verb other than
GET/HEAD/POST (such as DELETE) or that uses custom headers. To enable
pre-flighting, you must add a new OPTIONS handler for the route you want
to support:
var express = var cors = var app = appoptions'/products/:id' // enable pre-flight request for DELETE requestapp app
You can also enable pre-flight across-the-board like so:
appoptions'*' // include before other routes
Configuring CORS Asynchronously
var express = var cors = var app = var whitelist = 'http://example1.com' 'http://example2.com'var { var corsOptions; if whitelist !== -1 corsOptions = origin: true // reflect (enable) the requested origin in the CORS response else corsOptions = origin: false // disable CORS for this request // callback expects two parameters: error and options} app app
Configuration Options
origin
: Configures the Access-Control-Allow-Origin CORS header. Possible values:Boolean
- setorigin
totrue
to reflect the request origin, as defined byreq.header('Origin')
, or set it tofalse
to disable CORS.String
- setorigin
to a specific origin. For example if you set it to"http://example.com"
only requests from "http://example.com" will be allowed.RegExp
- setorigin
to a regular expression pattern which will be used to test the request origin. If it's a match, the request origin will be reflected. For example the pattern/example\.com$/
will reflect any request that is coming from an origin ending with "example.com".Array
- setorigin
to an array of valid origins. Each origin can be aString
or aRegExp
. For example["http://example1.com", /\.example2\.com$/]
will accept any request from "http://example1.com" or from a subdomain of "example2.com".Function
- setorigin
to a function implementing some custom logic. The function takes the request origin as the first parameter and a callback (which expects the signatureerr [object], allow [bool]
) as the second.
methods
: Configures the Access-Control-Allow-Methods CORS header. Expects a comma-delimited string (ex: 'GET,PUT,POST') or an array (ex:['GET', 'PUT', 'POST']
).allowedHeaders
: Configures the Access-Control-Allow-Headers CORS header. Expects a comma-delimited string (ex: 'Content-Type,Authorization') or an array (ex:['Content-Type', 'Authorization']
). If not specified, defaults to reflecting the headers specified in the request's Access-Control-Request-Headers header.exposedHeaders
: Configures the Access-Control-Expose-Headers CORS header. Expects a comma-delimited string (ex: 'Content-Range,X-Content-Range') or an array (ex:['Content-Range', 'X-Content-Range']
). If not specified, no custom headers are exposed.credentials
: Configures the Access-Control-Allow-Credentials CORS header. Set totrue
to pass the header, otherwise it is omitted.maxAge
: Configures the Access-Control-Max-Age CORS header. Set to an integer to pass the header, otherwise it is omitted.preflightContinue
: Pass the CORS preflight response to the next handler.optionsSuccessStatus
: Provides a status code to use for successfulOPTIONS
requests, since some legacy browsers (IE11, various SmartTVs) choke on204
.
The default configuration is the equivalent of:
For details on the effect of each CORS header, read this article on HTML5 Rocks.
Demo
A demo that illustrates CORS working (and not working) using jQuery is available here: http://node-cors-client.herokuapp.com/
Code for that demo can be found here:
- Client: https://github.com/TroyGoode/node-cors-client
- Server: https://github.com/TroyGoode/node-cors-server