source: trip-planner-front/node_modules/on-headers/README.md@ 6a3a178

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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
9Execute a listener when a response is about to write headers.
10
11## Installation
12
13This 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
26var onHeaders = require('on-headers')
27```
28
29### onHeaders(res, listener)
30
31This will add the listener `listener` to fire when headers are emitted for `res`.
32The listener is passed the `response` object as it's context (`this`). Headers are
33considered to be emitted only once, right before they are sent to the client.
34
35When this is called multiple times on the same `res`, the `listener`s are fired
36in the reverse order they were added.
37
38## Examples
39
40```js
41var http = require('http')
42var onHeaders = require('on-headers')
43
44http
45 .createServer(onRequest)
46 .listen(3000)
47
48function 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
55function 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
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