Export the default filter function for wrapping

closes #24

Author: dougwilson

HISTORY.md

@@ -1,6 +1,7 @@
 unreleased
 ==========
 
+  * Export the default `filter` function for wrapping
   * deps: accepts@~1.2.2
     - deps: mime-types@~2.0.7
     - deps: [email protected]

README.md

@@ -52,6 +52,25 @@ The byte threshold for the response body size before compression is considered
 for the response, defaults to `1kb`. This is a number of bytes, any string
 accepted by the [bytes](https://www.npmjs.com/package/bytes) module, or `false`.
 
+#### .filter
+
+The default `filter` function. This is used to construct a custom filter
+function that is an extension of the default function.
+
+```js
+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

index.js

@@ -25,6 +25,7 @@ var zlib = require('zlib')
  */
 
 module.exports = compression
+module.exports.filter = shouldCompress
 
 /**
  * Compress response data with gzip / deflate.

test/compression.js

@@ -394,6 +394,44 @@ describe('compression()', function(){
     })
   })
 
+  describe('.filter', function () {
+    it('should be a function', function () {
+      assert.equal(typeof compression.filter, 'function')
+    })
+
+    it('should return false on empty response', function (done) {
+      var server = http.createServer(function (req, res) {
+        res.end(String(compression.filter(req, res)))
+      })
+
+      request(server)
+      .get('/')
+      .expect(200, 'false', done)
+    })
+
+    it('should return true for "text/plain"', function (done) {
+      var server = http.createServer(function (req, res) {
+        res.setHeader('Content-Type', 'text/plain')
+        res.end(String(compression.filter(req, res)))
+      })
+
+      request(server)
+      .get('/')
+      .expect(200, 'true', done)
+    })
+
+    it('should return false for "application/x-bogus"', function (done) {
+      var server = http.createServer(function (req, res) {
+        res.setHeader('Content-Type', 'application/x-bogus')
+        res.end(String(compression.filter(req, res)))
+      })
+
+      request(server)
+      .get('/')
+      .expect(200, 'false', done)
+    })
+  })
+
   describe('res.flush()', function () {
     it('should always be present', function (done) {
       var server = createServer(null, function (req, res) {