how to get value on multiple line field using jquery in Sharepoint 2013

I'm trying to figure out how to get multiple lines field's value using jquery in Sharepoint 2013 form, but get blank response.  See my code below.

<script src ="../....../jquery-1.11.3.min.js"></script>

function PreSaveAction() {

  var x = $("input[id=ctl00_ctl42_g_.......]").text();

  alert(x);

  return true;

}

</script>

After I enter some text on the field and save the form, I received alert with blank entry.  This field is set required. 

Eventually, I want to set my own warning on the field if the field is blank.  Currently, I receive duplicated warnings 'you must specify a value for this required field'.

Thanks,

Jen