Answers for "jquery how to get checked checkbox value"

jquery checkbox is checked

//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 jquery checked

var isExpanded = $(this).attr('checked') == "checked";