Add is.generator() and is.generatorFunction() (#4)

index.js

@@ -82,6 +82,11 @@ const hasPromiseAPI = x =>
 
 is.promise = x => is.nativePromise(x) || hasPromiseAPI(x);
 
+is.generator = x => is.iterable(x) && is.function(x.next) && is.function(x.throw);
+
+// Change to use `isObjectOfType` once Node 4.x.x LTS is dropped
+is.generatorFunction = x => x.constructor.name === 'GeneratorFunction';
+
 is.regExp = isObjectOfType('RegExp');
 is.date = isObjectOfType('Date');
 is.error = isObjectOfType('Error');

readme.md

@@ -78,6 +78,12 @@ Keep in mind that [functions are objects too](https://developer.mozilla.org/en-U
 
 Returns `true` for any object with a `.then()` and `.catch()` method. Prefer this one over `.nativePromise()` as you usually want to allow userland promise implementations too.
 
+##### .generator(value)
+
+Returns `true` for any object that implements its own `.next()` and `.throw()` methods and has a function definition for `Symbol.iterator`.
+
+##### .generatorFunction(value)
+
 ##### .map(value)
 ##### .set(value)
 ##### .weakMap(value)

test.js

@@ -58,6 +58,9 @@ const types = new Map([
 		PromiseSubclassFixture.resolve()
 	]],
 	['promise', {then() {}, catch() {}}],
+	['generator', (function * () {
+		yield 42;
+	})()],
 	['map', new Map()],
 	['set', new Set()],
 	['weakMap', new WeakMap()],
@@ -86,7 +89,7 @@ const types = new Map([
 	['integer', 6]
 ]);
 
-// This ensure a certain method matches only the types
+// This ensures a certain method matches only the types
 // it's supposed to and none of the other methods' types
 const testType = (t, type, exclude) => {
 	for (const [key, value] of types) {
@@ -170,6 +173,17 @@ if (isNode8orHigher) {
 	});
 }
 
+test('is.generator', t => {
+	testType(t, 'generator', ['function']);
+});
+
+test('is.generatorFunction', t => {
+	const gen = function * () {
+		yield 42;
+	};
+	t.true(m.generatorFunction(gen));
+});
+
 test('is.map', t => {
 	testType(t, 'map');
 });