Add prototype to descriptions

snippets/isGeneratorFunction.md

@@ -5,7 +5,7 @@ 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]'`.
+- Use `Object.prototype.toString()` and `Function.prototype.call()` and check if the result is `'[object GeneratorFunction]'`.
 
 ```js
 const isGeneratorFunction = val =>