Here's an example of how to do conditional rendering in React:

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import React, { useState } from "react";

function App() {
  const [isLoggedIn, setIsLoggedIn] = useState(false);

  const handleLogin = () => {
    setIsLoggedIn(true);
  };

  const handleLogout = () => {
    setIsLoggedIn(false);
  };

  return (
    <div>
      {isLoggedIn ? (
        <button onClick={handleLogout}>Logout</button>
      ) : (
        <button onClick={handleLogin}>Login</button>
      )}
    </div>
  );
}

export default App;

In this example, we're using the useState hook to keep track of whether the user is logged in or not. We have two functions, handleLogin and handleLogout, which are called when the respective buttons are clicked.

The conditional rendering is done using a ternary operator to check if the user is logged in or not. If they are, we render a "Logout" button that will call the handleLogout function when clicked. If they're not logged in, we render a "Login" button that will call the handleLogin function when clicked.

This is just one example of how to do conditional rendering in React. There are many other ways to do it, depending on your specific use case.

To detect whether the user is accessing the app via a Mac or Windows system, you can check for the navigator.platform property. This property contains information about the operating system of the client.

Here's an example of how to do it in JavaScript:

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const isMac = navigator.platform.toUpperCase().indexOf('MAC') >= 0;

if (isMac) {
  // display cmd+enter shortcut
} else {
  // display ctrl+enter shortcut
}

You can then display the appropriate shortcut based on the result of the check.

To add a listener to trigger the form's submission when the user presses the shortcut, you can use the addEventListener method on the document object to listen for a keydown event. The keydown event provides information about which key was pressed.

Here's an example of how to do it in JavaScript:

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const form = document.getElementById('myForm');

document.addEventListener('keydown', (event) => {
  if ((isMac && event.metaKey && event.keyCode === 13) ||
      (!isMac && event.ctrlKey && event.keyCode === 13)) {
    form.submit();
  }
});

This code listens for the keydown event on the document, and when it detects the appropriate shortcut (cmd+enter for Mac or ctrl+enter for Windows), it submits the form. Note that event.metaKey is used for Mac and event.ctrlKey is used for Windows to check whether the command or control key was pressed. The keyCode property contains the code for the key that was pressed, and 13 is the code for the Enter key.

Here's an example of how it can be used in ReactJS:

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import React, { useEffect } from 'react';

function MyForm() {
  const isMac = navigator.platform.toUpperCase().indexOf('MAC') >= 0;

  useEffect(() => {
    const form = document.getElementById('myForm');

    const handleKeyDown = (event) => {
      if ((isMac && event.metaKey && event.keyCode === 13) ||
          (!isMac && event.ctrlKey && event.keyCode === 13)) {
        form.submit();
      }
    };

    document.addEventListener('keydown', handleKeyDown);

    return () => {
      document.removeEventListener('keydown', handleKeyDown);
    };
  }, [isMac]);

  return (
    <form id="myForm">
      {/* form fields and submit button here */}
    </form>
  );
}

In this example, the useEffect hook is used to add and remove the keydown event listener, and the isMac variable is passed as a dependency to the hook so that it will update if the user switches between Mac and Windows during the session.

To play a local audio file in a ReactJS app component, you can use the React Audio Player package. Here is an example of how to use it:

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import React from 'react';
import AudioPlayer from 'react-audio-player';

export default class App extends React.Component {
  render() {
    return (
      <div>
        <AudioPlayer
          src="my-audio-file.mp3"
          onPlay={(e) => console.log(e)}
        />
      </div>
    );
  }
}

The error message createRoot(...): Target container is not a DOM element indicates that you either explicitly provided a container that is not a DOM element or that you are trying to render something that needs a DOM element as the container. Make sure that the first argument of ReactDOM.createRoot is a DOM element. See the ReactDOM reference for more information.