checkbox-enabled-disabled

HTML

<div class="billing">
  <input type="checkbox" class="billing-checkbox" checked>
  <input type="button" value="Hello Javascript!">
</div>

JavaScript

$(document).ready(function() {
	$('.billing-checkbox').prop('checked', localStorage.getItem('buttonDisabled') !== "disabled");
	toggleBilling({
		target: $('.billing-checkbox')[0]
  })
  $('.billing-checkbox').on('change', toggleBilling);
});

function toggleBilling(e) {
	$('.billing input[type="button"]').attr('disabled', !e.target.checked)
	localStorage.setItem('buttonDisabled', $('.billing input[type="button"]').attr('disabled'));
}