title: How to get difference of changed input value?
body: <p>How can I get difference between old value and the changed one?</p>
  <pre><code>$('input[name =&quot;refresh&quot;]').on(&quot;change paste keyup&quot;, function() {
     ???
  });
  </code></pre>
  <p>So, this code (from another question) detects an input change, the input itself is number only, user set input's value from 10 to 25, how to get the difference between old and new values without pre-loading default values? By the way, default values bigger than 0.</p>