old_contents: function something()
  {
  	var x = window.localStorage.getItem('aaa');
  
  	window.localStorage.setItem('aaa', 555);
  
  	alert(x);
  }
  
new_contents: function something()
  {
  	var x = window.localStorage.getItem('aaa');
  
  	x = x*1 + 1;
  
  	window.localStorage.setItem('aaa', x);
  
  	alert(x);
  }
  
subject: Store x variable on client side