Add support for detecting transform streams (#4)

Fixes #3.

Author: kevva

index.js

@@ -15,3 +15,7 @@ isStream.readable = function (stream) {
 isStream.duplex = function (stream) {
 	return isStream.writable(stream) && isStream.readable(stream);
 };
+
+isStream.transform = function (stream) {
+	return isStream.duplex(stream) && typeof stream._transform === 'function' && typeof stream._transformState === 'object';
+};

readme.md

@@ -34,6 +34,7 @@ isStream({});
 
 #### isStream.duplex(stream)
 
+#### isStream.transform(stream)
 
 
 ## License

test.js

@@ -55,3 +55,14 @@ test('isStream.duplex()', t => {
 	t.false(m.duplex(fs.createReadStream('test.js')));
 	t.false(m.duplex(fs.createWriteStream(tempfile())));
 });
+
+test('isStream.transform()', t => {
+	t.true(m.transform(new Stream.Transform()));
+	t.true(m.transform(new Stream.PassThrough()));
+	t.false(m.transform(new Stream.Duplex()));
+	t.false(m.transform(new Stream.Stream()));
+	t.false(m.transform(new Stream.Readable()));
+	t.false(m.transform(new Stream.Writable()));
+	t.false(m.transform(fs.createReadStream('test.js')));
+	t.false(m.transform(fs.createWriteStream(tempfile())));
+});