How do I make sure a high score is emitted by the HTML page and not the client putting in console?

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Node.js

I have this function which pushes high scores onto the server

async function pushNewHighscore(score) {
	const req = await fetch('/createhighscore', {
		method: 'POST',
		headers: {
			'Content-Type': 'application/json'
		},
		body: JSON.stringify({
			score
		})
	});

	return req.status;
}

But this can be hacked using the console
How do I verify if the high score was actually hard-earned and not hacked
Here for all the code:
Space Chaos - Replit[^]

What I have tried:

Asking my full stack devolpers friends