So React added isReactComponent to Component class but the author doesn't explain why they couldn't just check for render() method. It works in this React-like library:
Someone else asked that same question on Reddit [0], and Dan pointed out the paragraph in the post that answers it :
> One other possible heuristic could be to check for presence of a render method on the prototype. However, at the time it wasn’t clear how the component API would evolve. Every check has a cost so we wouldn’t want to add more than one. This would also not work if render was defined as an instance method, such as with the class property syntax.
https://github.com/wisercoder/uibuilder/blob/master/UIBuilde...