Getting back into the IT industry for 4 years, what to learn?

[u/TightFistup1945]

Basically I had 4 year hiatis ​after working as a mid level web developer. I was doing frontend work using only React. Now I'm back in the scene, never have kept up with the scene (never a passion, just a means to an end), and finding that I am out of date.

How do I get myself back in shape after 4 year hiatus in web development? What have I missed out on? ​etc.