Add isGeneratorFunction

snippets/isGeneratorFunction.md

@@ -0,0 +1,18 @@
+---
+title: isGeneratorFunction
+tags: type,function,intermediate
+---
+
+Checks if the given argument is a generator function.
+
+Use `Object.prototype.toString()` and `Function.call()` and check if the result is `'[object GeneratorFunction]'`.
+
+```js
+const isGeneratorFunction = val =>
+  Object.prototype.toString.call(val) === '[object GeneratorFunction]';
+```
+
+```js
+isGeneratorFunction(function() {}); // false
+isGeneratorFunction(function*() {}); // true
+```