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compression

Node.js compression middleware.

Install

$ npm install compression

API

var compression = require('compression')

compression(options)

Returns the compression middleware using the given options.

app.use(compression({
  threshold: 512
}))

Options

threshold <1kb> - response is only compressed if the byte size is at or above this threshold.
filter - a filtering callback function. Uses Compressible by default.

In addition to these, zlib options may be passed in to the options object.

res.flush

This module adds a res.flush() method to force the partially-compressed response to be flushed to the client.

Examples

express/connect

When using this module with express or connect, simply app.use the module as high as you like. Requests that pass through the middleware will be compressed.

var compression = require('compression')
var express = require('express')

var app = express()

// compress all requests
app.use(compression())

// add alll routes

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.

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)
  })
})

License

MIT

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