Execute a listener when a response is about to write headers.
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README.md

on-headers

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Execute a listener when a response is about to write headers.

Installation

This is a Node.js module available through the npm registry. Installation is done using the npm install command:

$ npm install on-headers

API

var onHeaders = require('on-headers')

onHeaders(res, listener)

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 listeners are fired in the reverse order they were added.

Examples

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!')
}

Testing

$ npm test

License

MIT