function call in select option code example

Example 1: javascript prevent value change in select option

old_value = $('#select :selected').val();
$('#select').change(function() {
  if($(this).val() == 'option 3') {//your specific condition
     $('#select').val(old_value);
  } else {
    old_value = $('#select :selected').val();
  }
});

Example 2: javascript function call with variable

function abc() {
  alert('test');
}

var funcName = 'abc';

window[funcName]();