function something()
{
	var x = window.localStorage.getItem('bbb');

	x = x * 1 + 1;

	window.localStorage.setItem('bbb', x);

	alert('Hello ' + x + '!');	
}

function add_to_cart(id)
{
	alert('You addet pizza with id: ' + id);
}
@@ -61,17 +61,16 @@
 'bbb');%0A
-%0A
 %09x = x *
@@ -77,17 +77,16 @@
  1 + 1;%0A
-%0A
 %09window.
@@ -117,17 +117,16 @@
 b', x);%0A
-%0A
 %09alert('
@@ -181,46 +181,129 @@
 %0A%7B%0A%09
-alert('You addet pizza with id: ' + id
+var key = 'product_' + id;%0A%09var x = window.localStorage.getItem(key);%0A%09x = x * 1 + 1;%0A%09window.localStorage.setItem(key, x
 );%0A%7D

Update add_to_cart function