on-headers
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- Version published
- Maintainers
- 1
- Weekly downloads
- 19,889,285
- decreased by-7.71%
Weekly downloads
Package description
What is on-headers?
The on-headers npm package is used to execute custom logic when headers are about to be written to the response object in a Node.js HTTP server. This can be useful for logging, setting default headers, or performing other actions based on the headers before they are sent to the client.
What are on-headers's main functionalities?
Execute custom logic before headers are sent
This code sample demonstrates how to use the on-headers package to execute a function right before the headers are sent in an HTTP response. The function `onHeadersListener` is called just before the headers are written to the response.
const onHeaders = require('on-headers');
function onHeadersListener(res) {
console.log('Headers will be sent soon.');
// Perform any custom logic here
}
http.createServer(function (req, res) {
onHeaders(res, onHeadersListener);
res.setHeader('Content-Type', 'text/plain');
res.end('Hello World!');
});Other packages similar to on-headers
on-finished
The on-finished package is similar to on-headers in that it allows you to execute code based on HTTP request/response lifecycle events. However, on-finished is used to detect when the HTTP response has finished or when the request has been closed, rather than when headers are about to be sent.
prepend-http
While not directly similar to on-headers, prepend-http is another package that deals with HTTP headers. It is used to prepend `http://` to a URL if it's missing. This package does not provide hooks into the response object's lifecycle.
helmet
Helmet is a package that provides a set of middleware functions to set HTTP response headers for security purposes. It differs from on-headers as it focuses on security headers and provides a higher-level API for configuring them, rather than providing a hook for any kind of custom logic before headers are sent.
Readme
on-headers
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
FAQs
Execute a listener when a response is about to write headers
The npm package on-headers receives a total of 18,869,808 weekly downloads. As such, on-headers popularity was classified as popular.
We found that on-headers demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 1 open source maintainer collaborating on the project.
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