Black_Star,
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style type="text/css">
</style>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
<script>
$(function() {
function checkIndex(cls)
{
return [].reduce.call(document.querySelectorAll(cls), function(arr, elem, i) {
elem.checked && arr.push(i);
return arr
},[])
}
var checkedCheckBoxes = checkIndex(".bl_checkedColumn__checkbox")
alert(JSON.stringify(checkedCheckBoxes, null, 1));
});
</script>
</head>
<body>
<input class="bl_checkedColumn__checkbox" type="checkbox" checked>
<input class="bl_checkedColumn__checkbox" type="checkbox" checked>
<input class="bl_checkedColumn__checkbox" type="checkbox">
<input class="bl_checkedColumn__checkbox" type="checkbox" checked>
</body>
</html>