Numbers only

demo.html

<input type="text" numbers-only >
<script>
  document.addEventListener('DOMContentLoaded', function () {
	document.querySelectorAll('input[numbers-only]').forEach(function (input) {
		input.addEventListener('input', function () {
			input.value = input.value.replace(/[^.\d]+/g, '').replace(/^([^.]*\.)|\./g, '$1');
		});
	});
});
</script>

numbers-only.js

document.addEventListener('DOMContentLoaded', function () {
	document.querySelectorAll('input[numbers-only]').forEach(function (input) {
		input.addEventListener('input', function () {
			input.value = input.value.replace(/[^.\d]+/g, '').replace(/^([^.]*\.)|\./g, '$1');
		});
	});
});