Turn html lists into checklists; great for markdown

persistant_checklist.html

<script>
var checkboxes = [];
function getCheckboxStates() { return checkboxes.map(bx => !!bx.checked); };
function saveCheckboxStates() {
	localStorage['boxStates'] = JSON.stringify(getCheckboxStates());
}

// Add a checkbox in front of every list item, save reference to each
[].slice.call(document.getElementsByTagName('li')).forEach((li, index) => {
	var chkbx = document.createElement('input');
	chkbx.type = "checkbox";
	li.insertBefore(chkbx, li.firstChild);
	chkbx.addEventListener('click', saveCheckboxStates);
	checkboxes.push(chkbx);
});

// If there are no local-storage states, create them.
if (!localStorage['boxStates']){
	saveCheckboxStates();
// Apply the states saved in local-storage
} else {
	boxStates = JSON.parse(localStorage['boxStates']);
	checkboxes.forEach((chkbx, i) => {chkbx.checked = boxStates[i];});
}

</script>
<style>
ul { list-style-type: none; }
</style>