Edit in JSFiddle

$(document).ready(function(){
    
      $('h1').hide();

      $('[name=yourName]').on('input',function(e){
          e.preventDefault();
          var element = $(this);
          
          $('#theName').html(element.val());
          
          if(element.val() != ''){
              $('h1').show();
          }else{
              $('h1').hide();
          }    
          
      });
  });

<div>
  <label>Nombre:</label>
  <input type="text" name="yourName" placeholder="Introduce tu Nombre">
  <h1>Hola <span id="theName"></span>!</h1>
</div>