useConnection()

Source on GitHub 

The useConnection hook returns the current connection state when there is an active connection interaction. If no connection interaction is active, it returns null for every property. A typical use case for this hook is to colorize handles based on a certain condition (e.g. if the connection is valid or not).

import { useConnection } from '@xyflow/react';
 
export default function App() {
  const connection = useConnection();
 
  return (
    <div>
      {connection ? `Someone is trying to make a connection from ${connection.fromNode} to this one.` : 'There are currently no incoming connections!'}
    </div>
  );
}

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