http-cors

Middy CORS middleware

CORS middleware for the middy framework, the stylish Node.js middleware engine for AWS Lambda

This middleware sets HTTP CORS headers (Access-Control-Allow-Origin, Access-Control-Allow-Headers, Access-Control-Allow-Credentials), necessary for making cross-origin requests, to the response object.

Sets headers in after and onError phases.

Install

To install this middleware you can use NPM:

npm install --save @middy/http-cors

Options

• getOrigin (function(incomingOrigin:string, options)) (optional): take full control of the generating the returned origin. Defaults to using the origin or origins option.
• origin (string) (optional): origin to put in the header (default: "*")
• origins (array) (optional): An array of allowed origins. The incoming origin is matched against the list and is returned if present.
• headers (string) (optional): value to put in Access-Control-Allow-Headers (default: null)
• credentials (bool) (optional): if true, sets the Access-Control-Allow-Origin as request header Origin, if present (default false)
• maxAge (string) (optional): value to put in Access-Control-Max-Age header (default: null)
• cacheControl (string) (optional): value to put in Cache-Control header on pre-flight (OPTIONS) requests (default: null)

NOTES:

• If another middleware does not handle and swallow errors, then it will bubble all the way up and terminate the Lambda invocation with an error. In this case API Gateway would return a default 502 response, and the CORS headers would be lost. To prevent this, you should use the httpErrorHandler middleware before the cors middleware like this:

const middy = require('@middy/core')
const httpErrorHandler = require('@middy/http-error-handler')
const cors = require('@middy/http-cors')

const handler = middy((event, context, cb) => {
  throw new createError.UnprocessableEntity()
})
handler.use(httpErrorHandler())
       .use(cors())
           
// when Lambda runs the handler...
handler({}, {}, (_, response) => {
  expect(response.headers['Access-Control-Allow-Origin']).toEqual('*')
  expect(response).toEqual({
      statusCode: 422,
      body: 'Unprocessable Entity'
    })
})

Sample usage

const middy = require('@middy/core')
const { cors } = require('@middy/http-cors')

const handler = middy((event, context, cb) => {
  cb(null, {})
})

handler.use(cors())

// when Lambda runs the handler...
handler({}, {}, (_, response) => {
  expect(response.headers['Access-Control-Allow-Origin']).toEqual('*')
})

Middy documentation and examples

For more documentation and examples, refers to the main Middy monorepo on GitHub or Middy official website.

Contributing

Everyone is very welcome to contribute to this repository. Feel free to raise issues or to submit Pull Requests.

License

Licensed under MIT License. Copyright (c) 2017-2018 Luciano Mammino and the Middy team.