//using plane javascript
if(document.getElementById('on_or_off_checkbox').checked) {
//I am checked
}
//using jQuery
if($('#on_or_off_checkbox').is(':checked')){
//I am checked
}$("checkbox").is(":checked")// Check a checkbox
$(selector).prop('checked', true);
// Un-check a checkbox
$(selector).prop('checked', false);
// Determine if checked or not
isChecked = $(selector).prop('checked');if ($('#grepperRocks').is(':checked')) {
// this checkbox is checked
}$.each(arrayValues, function(i, val){
$("input[value='" + val + "']").prop('checked', true);
});
$('.myCheckbox')[0].checked = true;
$('.myCheckbox')[0].checked = false;