res: add .is()

docs/api/request.md

@@ -167,7 +167,7 @@ this.body = yield db.find('something');
   If `app.subdomainOffset` is not set, this.subdomains is `["ferrets", "tobi"]`.
   If `app.subdomainOffset` is 3, this.subdomains is `["tobi"]`.
 
-### req.is(type)
+### req.is(types...)
 
   Check if the incoming request contains the "Content-Type"
   header field, and it contains any of the give mime `type`s.
@@ -346,4 +346,3 @@ this.acceptsLanguages();
 ### req.get(field)
 
   Return request header.
-

docs/api/response.md

@@ -20,7 +20,7 @@
 
 ### res.status=
 
-  Set response status via numeric code or case-insensitive string:
+  Set response status via numeric code:
 
   - 100 "continue"
   - 101 "switching protocols"
@@ -182,6 +182,33 @@ this.type = 'png';
   when explicitly defined in full as `res.type = 'text/html'`
   no charset is assigned.
 
+### res.is(types...)
+
+  Very similar to `this.request.is()`.
+  Check whether the response type is one of the supplied types.
+  This is particularly useful for creating middleware that
+  change certain responses.
+
+  For example, this is a middleware that minifies
+  all HTML response except for streamss.
+
+```js
+var minify = require('html-minifier');
+
+app.use(function *minifyHTML(next){
+  yield* next;
+
+  if (!this.response.is('html')) return;
+
+  var body = this.response.body;
+  if (!body) return;
+  // too difficult to do this with a stream
+  if ('function' == typeof body.pipe) return;
+  if (Buffer.isBuffer(body)) body = body.toString('utf8');
+  this.response.body = minify(body);
+});
+```
+
 ### res.redirect(url, [alt])
 
   Perform a [302] redirect to `url`.

lib/response.js

@@ -8,6 +8,7 @@ var getType = require('mime-types').contentType;
 var isJSON = require('koa-is-json');
 var escape = require('escape-html');
 var onfinish = require('finished');
+var typeis = require('type-is').is;
 var status = require('statuses');
 var destroy = require('dethroy');
 var assert = require('assert');
@@ -338,6 +339,22 @@ module.exports = {
     return type.split(';')[0];
   },
 
+  /**
+   * Check whether the response is one of the listed types.
+   * Pretty much the same as `this.request.is()`.
+   *
+   * @param {String|Array} types...
+   * @return {String|false}
+   * @api public
+   */
+
+  is: function(types){
+    var type = this.type;
+    if (!types) return type || false;
+    if (!Array.isArray(types)) types = [].slice.call(arguments);
+    return typeis(type, types);
+  },
+
   /**
    * Return response header.
    *

test/response/is.js

@@ -0,0 +1,80 @@
+
+var context = require('../context');
+var should = require('should');
+var assert = require('assert');
+
+describe('response.is(type)', function(){
+  it('should ignore params', function(){
+    var res = context().response;
+    res.type = 'text/html; charset=utf-8';
+
+    res.is('text/*').should.equal('text/html');
+  })
+
+  describe('when no type is set', function(){
+    it('should return false', function(){
+      var res = context().response;
+
+      assert(false === res.is());
+      assert(false === res.is('html'));
+    })
+  })
+
+  describe('when given no types', function(){
+    it('should return the type', function(){
+      var res = context().response;
+      res.type = 'text/html; charset=utf-8';
+
+      res.is().should.equal('text/html');
+    })
+  })
+
+  describe('given one type', function(){
+    it('should return the type or false', function(){
+      var res = context().response;
+      res.type = 'image/png';
+
+      res.is('png').should.equal('png');
+      res.is('.png').should.equal('.png');
+      res.is('image/png').should.equal('image/png');
+      res.is('image/*').should.equal('image/png');
+      res.is('*/png').should.equal('image/png');
+
+      res.is('jpeg').should.be.false;
+      res.is('.jpeg').should.be.false;
+      res.is('image/jpeg').should.be.false;
+      res.is('text/*').should.be.false;
+      res.is('*/jpeg').should.be.false;
+    })
+  })
+
+  describe('given multiple types', function(){
+    it('should return the first match or false', function(){
+      var res = context().response;
+      res.type = 'image/png';
+
+      res.is('png').should.equal('png');
+      res.is('.png').should.equal('.png');
+      res.is('text/*', 'image/*').should.equal('image/png');
+      res.is('image/*', 'text/*').should.equal('image/png');
+      res.is('image/*', 'image/png').should.equal('image/png');
+      res.is('image/png', 'image/*').should.equal('image/png');
+
+      res.is('jpeg').should.be.false;
+      res.is('.jpeg').should.be.false;
+      res.is('text/*', 'application/*').should.be.false;
+      res.is('text/html', 'text/plain', 'application/json; charset=utf-8').should.be.false;
+    })
+  })
+
+  describe('when Content-Type: application/x-www-form-urlencoded', function(){
+    it('should match "urlencoded"', function(){
+      var res = context().response;
+      res.type = 'application/x-www-form-urlencoded';
+
+      res.is('urlencoded').should.equal('urlencoded');
+      res.is('json', 'urlencoded').should.equal('urlencoded');
+      res.is('urlencoded', 'json').should.equal('urlencoded');
+    })
+  })
+})