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81 lines
2.1 KiB
81 lines
2.1 KiB
# on-headers |
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[![NPM Version][npm-version-image]][npm-url] |
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[![NPM Downloads][npm-downloads-image]][npm-url] |
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[![Node.js Version][node-version-image]][node-version-url] |
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[![Build Status][travis-image]][travis-url] |
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[![Test Coverage][coveralls-image]][coveralls-url] |
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Execute a listener when a response is about to write headers. |
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## Installation |
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This is a [Node.js](https://nodejs.org/en/) module available through the |
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[npm registry](https://www.npmjs.com/). Installation is done using the |
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[`npm install` command](https://docs.npmjs.com/getting-started/installing-npm-packages-locally): |
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```sh |
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$ npm install on-headers |
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``` |
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## API |
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<!-- eslint-disable no-unused-vars --> |
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```js |
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var onHeaders = require('on-headers') |
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``` |
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### onHeaders(res, listener) |
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This will add the listener `listener` to fire when headers are emitted for `res`. |
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The listener is passed the `response` object as it's context (`this`). Headers are |
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considered to be emitted only once, right before they are sent to the client. |
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When this is called multiple times on the same `res`, the `listener`s are fired |
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in the reverse order they were added. |
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## Examples |
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```js |
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var http = require('http') |
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var onHeaders = require('on-headers') |
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http |
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.createServer(onRequest) |
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.listen(3000) |
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function addPoweredBy () { |
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// set if not set by end of request |
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if (!this.getHeader('X-Powered-By')) { |
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this.setHeader('X-Powered-By', 'Node.js') |
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} |
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} |
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function onRequest (req, res) { |
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onHeaders(res, addPoweredBy) |
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res.setHeader('Content-Type', 'text/plain') |
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res.end('hello!') |
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} |
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``` |
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## Testing |
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```sh |
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$ npm test |
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``` |
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## License |
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[MIT](LICENSE) |
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[coveralls-image]: https://badgen.net/coveralls/c/github/jshttp/on-headers/master |
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[coveralls-url]: https://coveralls.io/r/jshttp/on-headers?branch=master |
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[node-version-image]: https://badgen.net/npm/node/on-headers |
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[node-version-url]: https://nodejs.org/en/download |
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[npm-downloads-image]: https://badgen.net/npm/dm/on-headers |
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[npm-url]: https://npmjs.org/package/on-headers |
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[npm-version-image]: https://badgen.net/npm/v/on-headers |
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[travis-image]: https://badgen.net/travis/jshttp/on-headers/master |
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[travis-url]: https://travis-ci.org/jshttp/on-headers
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