I must disagree with the majority here.
Is React a fad? No. Fads are crazes that lack basis in their qualities and enthusiasm.
React is a tool that, for the time being, is one of the best answers to a set of complex challenges that are now facing UI engineers. As those challenges evolve over time it would be unreasonable to expect our tools to not evolve as well. React was engineered for a good reason and it's enjoying such wide usage because it contains the qualities that are needed. In other words, it's not a baseless craze but do expect it to change over time and eventually be replaced, like any tool.
I'd encourage you to be good at what you do, not merely satisfactory. Learn JS from top down and know how to use it without helpers. Then, learn React and as many other tools as you have time for, even if you have no plans to use them immediately. Being an engineer means having a hard and healthy work ethic. When you get a job you want your employer to genuinely feel like you're an indispensable part of the team. The more you know and can do the more you can help others and the open source community, and not just yourself. :)
Enjoy React!