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-`6` (currently what `zlib.Z_DEFAULT_COMPRESSION` points to).
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-`6` (currently what `zlib.constants.Z_DEFAULT_COMPRESSION` points to).
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-`7`
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-`8`
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-`9` Best compression (also `zlib.Z_BEST_COMPRESSION`).
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The default value is `zlib.Z_DEFAULT_COMPRESSION`, or `-1`.
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-`9` Best compression (also `zlib.constants.Z_BEST_COMPRESSION`).
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**Note** in the list above, `zlib` is from `zlib = require('zlib')`.
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##### memLevel
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Type: `Number`<br>
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Default: `zlib.constants.Z_DEFAULT_MEMLEVEL`, or `8`
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This specifies how much memory should be allocated for the internal compression
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state and is an integer in the range of `1` (minimum level) and `9` (maximum
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level).
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The default value is `zlib.Z_DEFAULT_MEMLEVEL`, or `8`.
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See [Node.js documentation](http://nodejs.org/api/zlib.html#zlib_memory_usage_tuning)
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regarding the usage.
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##### brotli
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Type: `Object`
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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.
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##### strategy
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Type: `Number`<br>
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Default: `zlib.constants.Z_DEFAULT_STRATEGY`
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This is used to tune the compression algorithm. This value only affects the
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compression ratio, not the correctness of the compressed output, even if it
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is not set appropriately.
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-`zlib.Z_DEFAULT_STRATEGY` Use for normal data.
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-`zlib.Z_FILTERED` Use for data produced by a filter (or predictor).
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-`zlib.constants.Z_DEFAULT_STRATEGY` Use for normal data.
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-`zlib.constants.Z_FILTERED` Use for data produced by a filter (or predictor).
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Filtered data consists mostly of small values with a somewhat random
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distribution. In this case, the compression algorithm is tuned to
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compress them better. The effect is to force more Huffman coding and less
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string matching; it is somewhat intermediate between `zlib.Z_DEFAULT_STRATEGY`
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and `zlib.Z_HUFFMAN_ONLY`.
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-`zlib.Z_FIXED` Use to prevent the use of dynamic Huffman codes, allowing
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string matching; it is somewhat intermediate between `zlib.constants.Z_DEFAULT_STRATEGY`
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and `zlib.constants.Z_HUFFMAN_ONLY`.
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-`zlib.constants.Z_FIXED` Use to prevent the use of dynamic Huffman codes, allowing
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for a simpler decoder for special applications.
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-`zlib.Z_HUFFMAN_ONLY` Use to force Huffman encoding only (no string match).
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-`zlib.Z_RLE` Use to limit match distances to one (run-length encoding).
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This is designed to be almost as fast as `zlib.Z_HUFFMAN_ONLY`, but give
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-`zlib.constants.Z_HUFFMAN_ONLY` Use to force Huffman encoding only (no string match).
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-`zlib.constants.Z_RLE` Use to limit match distances to one (run-length encoding).
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This is designed to be almost as fast as `zlib.constants.Z_HUFFMAN_ONLY`, but give
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better compression for PNG image data.
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**Note** in the list above, `zlib` is from `zlib = require('zlib')`.
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##### threshold
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Type: `Number` or `String`<br>
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Default: `1kb`
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The byte threshold for the response body size before compression is considered
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for the response, defaults to `1kb`. This is a number of bytes or any string
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for the response. This is a number of bytes or any string
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accepted by the [bytes](https://www.npmjs.com/package/bytes) module.
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**Note** this is only an advisory setting; if the response size cannot be determined
@@ -143,16 +158,18 @@ set a `Content-Length` response header.
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##### windowBits
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The default value is `zlib.Z_DEFAULT_WINDOWBITS`, or `15`.
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Type: `Number`<br>
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Default: `zlib.constants.Z_DEFAULT_WINDOWBITS`, or `15`
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See [Node.js documentation](http://nodejs.org/api/zlib.html#zlib_memory_usage_tuning)
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regarding the usage.
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##### enforceEncoding
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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.
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Type: `String`<br>
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Default: `identity`
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The default value is `identity`.
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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.
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#### .filter
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@@ -164,6 +181,7 @@ var compression = require('compression')
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var express =require('express')
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var app =express()
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app.use(compression({ filter: shouldCompress }))
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functionshouldCompress (req, res) {
@@ -184,9 +202,9 @@ response to be flushed to the client.
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## Examples
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### express/connect
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### express
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When using this module with express or connect, simply `app.use` the module as
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When using this module with express, simply `app.use` the module as
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high as you like. Requests that pass through the middleware will be compressed.
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```js
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// add all routes
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```
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### Node.js HTTP server
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```js
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var compression =require('compression')({ threshold:0 })
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var http =require('http')
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functioncreateServer (fn) {
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returnhttp.createServer(function (req, res) {
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compression(req, res, function (err) {
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if (err) {
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res.statusCode=err.status||500
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res.end(err.message)
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return
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}
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fn(req, res)
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})
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})
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}
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var server =createServer(function (req, res) {
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res.setHeader('Content-Type', 'text/plain')
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res.end('hello world!')
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})
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server.listen(3000, () => {
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console.log('> Listening at http://localhost:3000')
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})
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```
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### Server-Sent Events
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Because of the nature of compression this module does not work out of the box
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})
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```
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## Contributing
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The Express.js project welcomes all constructive contributions. Contributions take many forms,
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from code for bug fixes and enhancements, to additions and fixes to documentation, additional
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tests, triaging incoming pull requests and issues, and more!
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See the [Contributing Guide](https://github.com/expressjs/express/blob/master/Contributing.md) for more technical details on contributing.
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