I don't know JavaScript but ReactJS
Isn’t it weird to witness such a scenario where someone can code the ReactJS component but when you ask them to bind an onClick event in Vanilla JavaScript they can’t?
It’s been more than 5 years since I am taking interviews for front-end developers and gradually the trend is changing towards Frameworks/Libraries.
I am not against using any library or framework, I know it makes your development cycle faster and gives you some kind of pre-defined architecture where you can follow best practices but we shouldn’t forget the basics.
BASICS OF JAVASCRIPT
People find JavaScript a bit tricky language to learn. Keep in mind, all these frameworks and libraries are also built on JavaScript and if you want to get more out of it you need to learn the basics.
I would suggest directly starting with ES6 (ECMAScript) since the latest browsers support it and you can use a transcompiler like Babel if you need to support legacy browsers.
Organization’s point of view
Client awareness: If your clients are coming with such asks to implement a new framework or library, it’s a good opportunity to do quick requirements check instead of directly jumping on implementation.
Create needs: I believe in enabling people to work on basics instead of running behind fancy frameworks. There is no harm/shame when someone is working on a vanilla JavaScript project, so start discussing new ES12 features.