How to make an addition instead of a concatenation
<p>I have an input button. I created for this input an attribute called "multiplicateur" which has the value of 1. When the button is clicked I have a <code>.click()</code> triggered. The function is suppose to get the value of the attribute and add 1 to it. So my output should be 2. Instead the output is 11. It seems the system makes a concatenation instead of an addition.</p>

<p>My HTML:</p>

<pre><code>&lt;input id="envoyer" type="submit" multiplicateur=1&gt;
</code></pre>

<p>My JS:</p>

<pre><code>$('#envoyer').click(function() {
    var ajaxData = $(this).attr('multiplicateur');
    alert(ajaxData + 1);
});
</code></pre>
