Detect if the text field is empty or not, and run the code once, unless the state changes

I want to determine if this text field is empty or not, and then run some code on it.

Question: how can I run the code only once ... and then run it once every time the state of the text field changes for onefocus

• Different states: emptyor not empty.

Further development:

(The most important part of these jsfiddle is shown on the console.)

• Here is a jsfiddle of code that executes the code each (not what I want. Only the source code.).

  $('input').on("keyup", function() {
  
      var val = $(this).attr('value'),
          previous = $(this).prev();
  
      if ( val === '' ) {
          console.log('Empty');
      }
      else if ( val !== '' ) {
          console.log('Text');
      }
  
  });
  

• And here is a jsfiddle of code that executes the code once per focus (this is somewhat close to what I want).

  , , , . ?

  $('input').on("focus", function() {
  
      $('input').one("keyup", function() {
  
          var val = $(this).attr('value'),
              previous = $(this).prev();
  
          if ( val === '' ) {
              console.log('Empty');
          }
          else if ( val !== '' ) {
              console.log('Text');
          }
  
      });
  
  });