patch-headers

Express middleware to patch response headers written by another handler or middleware.

Usage

The module returns a function to build a middleware. The function must be called with a single options object with one or more of the following properties:

• allow: An array that contains a whitelist of header names.
• remove: An array that contains a blacklist of header names.
• static: An object with key value pairs of static header names and values.
• callback: A function which has a single object parameter for the header key value pairs and returns an object in the same format.

Priority:

1. If allow is set, all headers other than the ones in allow are removed
2. If remove is set, all headers in remove are removed
3. If static is set, all key: value in static are added
4. If callback is set, all key: value in callback(headers) are added

By this logic, using a combination of allow and remove doesn't make much sense.

Example

// load the module
const patchHeaders = require('patchHeaders')

// add the routing
app.use(patchHeaders({
  allow: ['Content-Length', 'Content-Type'],
  static: {
    'Access-Control-Allow-Origin': '*'
  },
  callback (headers) {
    return {
      'Content-Length': headers['Content-Length'] + Math.random()
    }
  }
})