//using plane javascript
if(document.getElementById('on_or_off_checkbox').checked) {
//I am checked
}
//using jQuery
if($('#on_or_off_checkbox').is(':checked')){
//I am checked
}if ($('#check_id').is(":checked"))
{
// it is checked
}// jQuery version 1.6 or above use:
$("#myRadioID").prop("checked", true);
//jQuery versions below 1.6 use:
$("#myRadioID").attr('checked', 'checked');$("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');// Check #x
$( "#x" ).prop( "checked", true );
// Uncheck #x
$( "#x" ).prop( "checked", false );