311 lines
9.7 KiB
Markdown
311 lines
9.7 KiB
Markdown
# compression
|
|
|
|
[![NPM Version][npm-image]][npm-url]
|
|
[![NPM Downloads][downloads-image]][downloads-url]
|
|
[![Build Status][github-actions-ci-image]][github-actions-ci-url]
|
|
[![OpenSSF Scorecard Badge][ossf-scorecard-badge]][ossf-scorecard-visualizer]
|
|
[![Funding][funding-image]][funding-url]
|
|
|
|
|
|
Node.js compression middleware.
|
|
|
|
The following compression codings are supported:
|
|
|
|
- deflate
|
|
- gzip
|
|
- br (brotli)
|
|
|
|
**Note** Brotli is supported only since Node.js versions v11.7.0 and v10.16.0.
|
|
|
|
## Install
|
|
|
|
This is a [Node.js](https://nodejs.org/en/) module available through the
|
|
[npm registry](https://www.npmjs.com/). Installation is done using the
|
|
[`npm install` command](https://docs.npmjs.com/getting-started/installing-npm-packages-locally):
|
|
|
|
```bash
|
|
$ npm install compression
|
|
```
|
|
|
|
## API
|
|
|
|
```js
|
|
var compression = require('compression')
|
|
```
|
|
|
|
### compression([options])
|
|
|
|
Returns the compression middleware using the given `options`. The middleware
|
|
will attempt to compress response bodies for all requests that traverse through
|
|
the middleware, based on the given `options`.
|
|
|
|
This middleware will never compress responses that include a `Cache-Control`
|
|
header with the [`no-transform` directive](https://tools.ietf.org/html/rfc7234#section-5.2.2.4),
|
|
as compressing will transform the body.
|
|
|
|
#### Options
|
|
|
|
`compression()` accepts these properties in the options object. In addition to
|
|
those listed below, [zlib](https://nodejs.org/api/zlib.html) options may be
|
|
passed in to the options object or
|
|
[brotli](https://nodejs.org/api/zlib.html#zlib_class_brotlioptions) options.
|
|
|
|
##### chunkSize
|
|
|
|
Type: `Number`<br>
|
|
Default: `zlib.constants.Z_DEFAULT_CHUNK`, or `16384`.
|
|
|
|
See [Node.js documentation](https://nodejs.org/api/zlib.html#zlib_memory_usage_tuning)
|
|
regarding the usage.
|
|
|
|
##### filter
|
|
|
|
Type: `Function`
|
|
|
|
A function to decide if the response should be considered for compression.
|
|
This function is called as `filter(req, res)` and is expected to return
|
|
`true` to consider the response for compression, or `false` to not compress
|
|
the response.
|
|
|
|
The default filter function uses the [compressible](https://www.npmjs.com/package/compressible)
|
|
module to determine if `res.getHeader('Content-Type')` is compressible.
|
|
|
|
##### level
|
|
|
|
Type: `Number`<br>
|
|
Default: `zlib.constants.Z_DEFAULT_COMPRESSION`, or `-1`
|
|
|
|
The level of zlib compression to apply to responses. A higher level will result
|
|
in better compression, but will take longer to complete. A lower level will
|
|
result in less compression, but will be much faster.
|
|
|
|
This is an integer in the range of `0` (no compression) to `9` (maximum
|
|
compression). The special value `-1` can be used to mean the "default
|
|
compression level", which is a default compromise between speed and
|
|
compression (currently equivalent to level 6).
|
|
|
|
- `-1` Default compression level (also `zlib.constants.Z_DEFAULT_COMPRESSION`).
|
|
- `0` No compression (also `zlib.constants.Z_NO_COMPRESSION`).
|
|
- `1` Fastest compression (also `zlib.constants.Z_BEST_SPEED`).
|
|
- `2`
|
|
- `3`
|
|
- `4`
|
|
- `5`
|
|
- `6` (currently what `zlib.constants.Z_DEFAULT_COMPRESSION` points to).
|
|
- `7`
|
|
- `8`
|
|
- `9` Best compression (also `zlib.constants.Z_BEST_COMPRESSION`).
|
|
|
|
**Note** in the list above, `zlib` is from `zlib = require('zlib')`.
|
|
|
|
##### memLevel
|
|
|
|
Type: `Number`<br>
|
|
Default: `zlib.constants.Z_DEFAULT_MEMLEVEL`, or `8`
|
|
|
|
This specifies how much memory should be allocated for the internal compression
|
|
state and is an integer in the range of `1` (minimum level) and `9` (maximum
|
|
level).
|
|
|
|
See [Node.js documentation](https://nodejs.org/api/zlib.html#zlib_memory_usage_tuning)
|
|
regarding the usage.
|
|
|
|
##### brotli
|
|
|
|
Type: `Object`
|
|
|
|
This specifies the options for configuring Brotli. See [Node.js documentation](https://nodejs.org/api/zlib.html#class-brotlioptions) for a complete list of available options.
|
|
|
|
|
|
##### strategy
|
|
|
|
Type: `Number`<br>
|
|
Default: `zlib.constants.Z_DEFAULT_STRATEGY`
|
|
|
|
This is used to tune the compression algorithm. This value only affects the
|
|
compression ratio, not the correctness of the compressed output, even if it
|
|
is not set appropriately.
|
|
|
|
- `zlib.constants.Z_DEFAULT_STRATEGY` Use for normal data.
|
|
- `zlib.constants.Z_FILTERED` Use for data produced by a filter (or predictor).
|
|
Filtered data consists mostly of small values with a somewhat random
|
|
distribution. In this case, the compression algorithm is tuned to
|
|
compress them better. The effect is to force more Huffman coding and less
|
|
string matching; it is somewhat intermediate between `zlib.constants.Z_DEFAULT_STRATEGY`
|
|
and `zlib.constants.Z_HUFFMAN_ONLY`.
|
|
- `zlib.constants.Z_FIXED` Use to prevent the use of dynamic Huffman codes, allowing
|
|
for a simpler decoder for special applications.
|
|
- `zlib.constants.Z_HUFFMAN_ONLY` Use to force Huffman encoding only (no string match).
|
|
- `zlib.constants.Z_RLE` Use to limit match distances to one (run-length encoding).
|
|
This is designed to be almost as fast as `zlib.constants.Z_HUFFMAN_ONLY`, but give
|
|
better compression for PNG image data.
|
|
|
|
**Note** in the list above, `zlib` is from `zlib = require('zlib')`.
|
|
|
|
##### threshold
|
|
|
|
Type: `Number` or `String`<br>
|
|
Default: `1kb`
|
|
|
|
The byte threshold for the response body size before compression is considered
|
|
for the response. This is a number of bytes or any string
|
|
accepted by the [bytes](https://www.npmjs.com/package/bytes) module.
|
|
|
|
**Note** this is only an advisory setting; if the response size cannot be determined
|
|
at the time the response headers are written, then it is assumed the response is
|
|
_over_ the threshold. To guarantee the response size can be determined, be sure
|
|
set a `Content-Length` response header.
|
|
|
|
##### windowBits
|
|
|
|
Type: `Number`<br>
|
|
Default: `zlib.constants.Z_DEFAULT_WINDOWBITS`, or `15`
|
|
|
|
See [Node.js documentation](https://nodejs.org/api/zlib.html#zlib_memory_usage_tuning)
|
|
regarding the usage.
|
|
|
|
##### enforceEncoding
|
|
|
|
Type: `String`<br>
|
|
Default: `identity`
|
|
|
|
This is the default encoding to use when the client does not specify an encoding in the request's [Accept-Encoding](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Accept-Encoding) header.
|
|
|
|
#### .filter
|
|
|
|
The default `filter` function. This is used to construct a custom filter
|
|
function that is an extension of the default function.
|
|
|
|
```js
|
|
var compression = require('compression')
|
|
var express = require('express')
|
|
|
|
var app = express()
|
|
|
|
app.use(compression({ filter: shouldCompress }))
|
|
|
|
function shouldCompress (req, res) {
|
|
if (req.headers['x-no-compression']) {
|
|
// don't compress responses with this request header
|
|
return false
|
|
}
|
|
|
|
// fallback to standard filter function
|
|
return compression.filter(req, res)
|
|
}
|
|
```
|
|
|
|
### res.flush
|
|
|
|
This module adds a `res.flush()` method to force the partially-compressed
|
|
response to be flushed to the client.
|
|
|
|
## Examples
|
|
|
|
### express
|
|
|
|
When using this module with express, simply `app.use` the module as
|
|
high as you like. Requests that pass through the middleware will be compressed.
|
|
|
|
```js
|
|
var compression = require('compression')
|
|
var express = require('express')
|
|
|
|
var app = express()
|
|
|
|
// compress all responses
|
|
app.use(compression())
|
|
|
|
// add all routes
|
|
```
|
|
|
|
### Node.js HTTP server
|
|
|
|
```js
|
|
var compression = require('compression')({ threshold: 0 })
|
|
var http = require('http')
|
|
|
|
function createServer (fn) {
|
|
return http.createServer(function (req, res) {
|
|
compression(req, res, function (err) {
|
|
if (err) {
|
|
res.statusCode = err.status || 500
|
|
res.end(err.message)
|
|
return
|
|
}
|
|
|
|
fn(req, res)
|
|
})
|
|
})
|
|
}
|
|
|
|
var server = createServer(function (req, res) {
|
|
res.setHeader('Content-Type', 'text/plain')
|
|
res.end('hello world!')
|
|
})
|
|
|
|
server.listen(3000, () => {
|
|
console.log('> Listening at http://localhost:3000')
|
|
})
|
|
```
|
|
|
|
### Server-Sent Events
|
|
|
|
Because of the nature of compression this module does not work out of the box
|
|
with server-sent events. To compress content, a window of the output needs to
|
|
be buffered up in order to get good compression. Typically when using server-sent
|
|
events, there are certain block of data that need to reach the client.
|
|
|
|
You can achieve this by calling `res.flush()` when you need the data written to
|
|
actually make it to the client.
|
|
|
|
```js
|
|
var compression = require('compression')
|
|
var express = require('express')
|
|
|
|
var app = express()
|
|
|
|
// compress responses
|
|
app.use(compression())
|
|
|
|
// server-sent event stream
|
|
app.get('/events', function (req, res) {
|
|
res.setHeader('Content-Type', 'text/event-stream')
|
|
res.setHeader('Cache-Control', 'no-cache')
|
|
|
|
// send a ping approx every 2 seconds
|
|
var timer = setInterval(function () {
|
|
res.write('data: ping\n\n')
|
|
|
|
// !!! this is the important part
|
|
res.flush()
|
|
}, 2000)
|
|
|
|
res.on('close', function () {
|
|
clearInterval(timer)
|
|
})
|
|
})
|
|
```
|
|
|
|
## Contributing
|
|
|
|
The Express.js project welcomes all constructive contributions. Contributions take many forms,
|
|
from code for bug fixes and enhancements, to additions and fixes to documentation, additional
|
|
tests, triaging incoming pull requests and issues, and more!
|
|
|
|
See the [Contributing Guide](https://github.com/expressjs/express/blob/master/Contributing.md) for more technical details on contributing.
|
|
|
|
## License
|
|
|
|
[MIT](LICENSE)
|
|
|
|
[npm-image]: https://badgen.net/npm/v/compression
|
|
[npm-url]: https://npmjs.org/package/compression
|
|
[downloads-image]: https://badgen.net/npm/dm/compression
|
|
[downloads-url]: https://npmcharts.com/compare/compression?minimal=true
|
|
[github-actions-ci-image]: https://badgen.net/github/checks/expressjs/compression/master?label=CI
|
|
[github-actions-ci-url]: https://github.com/expressjs/compression/actions?query=workflow%3Aci
|
|
[ossf-scorecard-badge]: https://api.scorecard.dev/projects/github.com/expressjs/compression/badge
|
|
[ossf-scorecard-visualizer]: https://ossf.github.io/scorecard-visualizer/#/projects/github.com/expressjs/compression
|
|
[funding-url]: https://opencollective.com/express
|
|
[funding-image]: https://badgen.net/badge/icon/sponsor/pink?icon=github&label=Open%20Collective |