Answers for "if checkbox is checked get value jquery"

jquery check if 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
}

jquery checkbox checked value

if ($('#check_id').is(":checked"))
{
  // it is checked
}