[nate_martin]

It's a little annoying when companies put framework names in their job titles. Asking for a "react engineer" or a "boost programmer" will likely turn away a lot of people who would actually be a good fit for the role. My suggestion is to just be open with the company and tell them what you do know and how quickly you can get up to speed. Something like: "I haven't used React on a paid project before, but I have a lot of experience with other frontend frameworks like x/y."

[WalterSear]

Chances are that the gatekeeper won't know enough to be interested.

[Kluny]

You have to get past ignorant gatekeepers. Do some google stalking to find out who's in charge of the team you want to join, and reach out on social media to let them know you'll be applying. Then include "so and so is expecting my application" when you send it to HR. Or something like that.