I have a very basic question with global variable and Jquery.

Here i is a counter. I want to know its last value and keep it out of the function

2. <div class="aremplir">
3. </div>
4. <button type="button" id="ajouter">Ajouter</button>
5. 
   
6. <script type="text/javascript">
7.     jQuery(function($){
8.  var i = 0;
9.   $('#ajouter').click(function(e){
10.       e.preventDefault();
11.       var content = "<div id='input_name"+i+"'><input type='text' /></div>";
12.       i++;
13.       $('.aremplir').append(content);
14.       mon_dernier_i = i;
15.   });
16. 
    
17.  if(typeof mon_dernier_i !='undefined'){
18.   console.log(mon_dernier_i);
19. }
20. });
21. 
    
22. </script> 

it seems that mon_dernier_i is not defined : nothing happens. I thought that not declaring 'var' in the function would make 'mon_dernier_i' global but obviously I am wrong...

Can anyone explain it to me ? 

Thank you very much