Why do I get 'React is not defined' with a CDN setup?
Either the React script did not load, or your code ran before the script loaded. Make sure the script tags are placed before your code and that you have an internet connection so the CDN loads.
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More FAQs in Common Errors When Setting Up React via CDN and How to Fix Them
You are using an old version of ReactDOM that only had ReactDOM.render. createRoot was introduced in React 18. Update your CDN scripts to React 18 or newer to use it.
Regular script tags do not understand JSX. You need to add type='text/babel' to the script and include the Babel standalone script, or use a build tool that compiles JSX for you.
Usually the root element id does not match what your script is targeting, or your JSX returns nothing. Verify the element exists and that your render call points to the correct root.
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