Execute a listener when a response is about to write headers.
This is a Node.js module available through the npm registry. Installation is done using the npm install
command:
$ npm install on-headers
var onHeaders = require('on-headers')
This will add the listener listener
to fire when headers are emitted for res
. The listener is passed the response
object as it's context (this
). Headers are considered to be emitted only once, right before they are sent to the client.
When this is called multiple times on the same res
, the listener
s are fired in the reverse order they were added.
var http = require('http') var onHeaders = require('on-headers') http .createServer(onRequest) .listen(3000) function addPoweredBy () { // set if not set by end of request if (!this.getHeader('X-Powered-By')) { this.setHeader('X-Powered-By', 'Node.js') } } function onRequest (req, res) { onHeaders(res, addPoweredBy) res.setHeader('Content-Type', 'text/plain') res.end('hello!') }
$ npm test