vapr-compress

Installation

npm install --save vapr
npm install --save vapr-compress

Usage

This plugin applies standard compression to Vapr responses.

const compress = require('vapr-compress');
const app = require('vapr')();
const route = app.get('/foo');

route.use(compress());
route.use((req) => {
  return [['hello world']]; // This will be gzipped
});

Details

This plugin utilizes content negotiation to decide when to compress a response. It will try to use the Transfer-Encoding header if supported by the client (as indicated by the TE header), but will fallback to the Content-Encoding/Accept-Encoding headers when necessary. Both the gzip and deflate encodings are supported, but gzip will be prioritized when the client has not indicated a preference.

If the response body is null or undefined, compression will be skipped. However, empty strings and buffers are still considered eligible (for the sake of cache coherence, response size is not taken into consideration by default). Compression is also skipped for HEAD requests, but headers are still set as if it were a GET request.

Unless the forced option is used or the only option is set to "transfer-encoding", the Vary header will be automatically updated to make caches aware of the content negotiation.

Options

Any options passed to the plugin are forwarded to the zlib core module. In addition, the behavior of the plugin can be customized with the options below.

options.only = null

This option is used to restrict compression to either "content-encoding" or "transfer-encoding", disabling the opposite style.

route.use(compress({ only: 'transfer-encoding' }));

options.aggressive = false

By default, if the client doesn't provide any content negotiation headers, compression will be skipped. However, if aggressive is true, compression (Content-Encoding) will be used in such cases.

route.use(compress({ aggressive: true }));

Since the aggressive option modifies the behavior of Content-Encoding compression, it cannot be used when the only option is set to "transfer-encoding".

options.forced = null

This option is used to bypass content negotiation. It can be set to either "content-encoding" or "transfer-encoding", indicating which style of compression to use.

route.use(compress({ forced: 'content-encoding' }));

Since the aggressive and only options modify the behavior of content negotiation but the forced option turns off content negotiation entirely, the neither of the former options can be used in combination with forced.

options.anyStatus = false

The default behavior is to skip responses that have a status code of 300 or higher. If this option is set to true, however, responses of any status code will be eligible for compression.

route.use(compress({ anyStatus: true }));

options.condition = null

Optionally, a condition function can be provided to bypass compression on a per-request basis. For each eligible request, the function will be invoked with request and response as arguments. If the function does not return true, compression will be skipped for that request.

route.use(compress({
  anyStatus: true,
  condition: (req, res) => res.code < 500,
}));