concatenating id and javascript value

concatenating id and javascript value

I'm trying to run this line of code, but I'm sure I'm doing something wrong. Can someone help me out? Specifically stuck on the "('#year' + lineNo)" part
Thanks
Mike

var lineNo = 4;
$('#year' + lineNo).change(function() {
  if($.trim($('#lname' + lineNo).val()) != '' && $.trim($('#fname' + lineNo).val()) != '' && $.trim($('#year' + lineNo).val()) != '') {
    $('#fields').addNewLine();
  }
});