testing new parallax image
[josuexyz/.git] / node_modules / on-headers / README.md
1 # on-headers
2
3 [![NPM Version][npm-version-image]][npm-url]
4 [![NPM Downloads][npm-downloads-image]][npm-url]
5 [![Node.js Version][node-version-image]][node-version-url]
6 [![Build Status][travis-image]][travis-url]
7 [![Test Coverage][coveralls-image]][coveralls-url]
8
9 Execute a listener when a response is about to write headers.
10
11 ## Installation
12
13 This is a [Node.js](https://nodejs.org/en/) module available through the
14 [npm registry](https://www.npmjs.com/). Installation is done using the
15 [`npm install` command](https://docs.npmjs.com/getting-started/installing-npm-packages-locally):
16
17 ```sh
18 $ npm install on-headers
19 ```
20
21 ## API
22
23 <!-- eslint-disable no-unused-vars -->
24
25 ```js
26 var onHeaders = require('on-headers')
27 ```
28
29 ### onHeaders(res, listener)
30
31 This will add the listener `listener` to fire when headers are emitted for `res`.
32 The listener is passed the `response` object as it's context (`this`). Headers are
33 considered to be emitted only once, right before they are sent to the client.
34
35 When this is called multiple times on the same `res`, the `listener`s are fired
36 in the reverse order they were added.
37
38 ## Examples
39
40 ```js
41 var http = require('http')
42 var onHeaders = require('on-headers')
43
44 http
45   .createServer(onRequest)
46   .listen(3000)
47
48 function addPoweredBy () {
49   // set if not set by end of request
50   if (!this.getHeader('X-Powered-By')) {
51     this.setHeader('X-Powered-By', 'Node.js')
52   }
53 }
54
55 function onRequest (req, res) {
56   onHeaders(res, addPoweredBy)
57
58   res.setHeader('Content-Type', 'text/plain')
59   res.end('hello!')
60 }
61 ```
62
63 ## Testing
64
65 ```sh
66 $ npm test
67 ```
68
69 ## License
70
71 [MIT](LICENSE)
72
73 [coveralls-image]: https://badgen.net/coveralls/c/github/jshttp/on-headers/master
74 [coveralls-url]: https://coveralls.io/r/jshttp/on-headers?branch=master
75 [node-version-image]: https://badgen.net/npm/node/on-headers
76 [node-version-url]: https://nodejs.org/en/download
77 [npm-downloads-image]: https://badgen.net/npm/dm/on-headers
78 [npm-url]: https://npmjs.org/package/on-headers
79 [npm-version-image]: https://badgen.net/npm/v/on-headers
80 [travis-image]: https://badgen.net/travis/jshttp/on-headers/master
81 [travis-url]: https://travis-ci.org/jshttp/on-headers