Uncaught ReferenceError: React is not defined

Question

I am trying to make ReactJS work with rails using this tutorial. I am getting this error:

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Uncaught ReferenceError: React is not defined

Answer 1

If you are using Babel and React 17, you might need to add "runtime2: "automatic" to config.

 {
     "presets": ["@babel/preset-env", ["@babel/preset-react", {
        "runtime": "automatic"
     }]]
 }