How to use $(this) keyword with multiple jQuery selections

I have these lines of jquery code, selecting a checkbox and a text area with a class selector. then, I want to deal with each one of them with $(this) keyword. I wrote this line for the checkbox and it's working

$(this).is(":checked")

and those lines for the text area but it's not working

$(this).val('');
$(this).prop("disabled", true);
$(this).prop("disabled", false);

what is the right way to implement such a code with $(this) keyword. this is the whole section of code:

$(".checkbox_class, .textarea_class").on("change", function()
{
    if( $(this).is(":checked") )
    {
        $(this).val('');
        $(this).prop("disabled", true);
    }
    else
        $(this).prop("disabled", false);
});