Answers for "jquery get checked value of checkbox"

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
}

jquery change the label of a value in select

$("#FIELDID").find("option:contains(\"OptionLabel\")").text('NewLabel');