Existing solutions already exist, but unfortunately search results are dominated by W3schools. Poor code examples and wrong information is why http://promotejs.com/ started. This is nothing new, the web needs nothing new. Learning about any modern web technology can be found online, but unfortunately people still venture into w3schools since it's top ranking.

Also their exams are unethical and should be treated as fraud. If you know anything about any of the topics, take their pre-exam and see for yourself.