js-runtime/example.html

<script src="runtime-checker.js"></script>

<script>
	const sum = typedFunction((a_number, b_number) => {
		return a + b;
	});

	const result = sum(1, 2);
	console.log(result); // 3

	sum("1", 2); // Error

</script>

<script>
	typedVar("test", 5);

	test = 6;

	test = "a string"; // Error
</script>