jQuery: if key "someKey" pressed
i know that i can detect a key, which has been pressed with the following code:

    $('input').keyup(function (e){
    if(e.keyCode == 13){
        alert('enter');
      }
    })

But i need to know if any key was pressed.
pseudocode:

    if ($('input').keyup() == true)
      { 
          doNothing();
      }
      else {
          doSomething();
      }

How can I do that?
jQuery: if key "someKey" pressed
===

i know that i can detect a key, which has been pressed with the following code:

    $('input').keyup(function (e){
    if(e.keyCode == 13){
        alert('enter');
      }
    })

But i need to know if any key was pressed.
pseudocode:

    if ($('input').keyup() == true)
      { 
          doNothing();
      }
      else {
          doSomething();
      }

How can I do that?