title: jquery keyup detect paste text from input
body: <p>I have to use here jquery keyup to detect if user enter any text or not, but my problem is if user use paste the text using <strong>mouse</strong>, it won't be able to detect it, can you tell me the reason?</p>
  
  <p>here is my source code:</p>
  
  <pre><code>$("textarea").keyup(function(){
          if($(this).val().length !== 0){
              $('#submit').attr('disabled',false);
  </code></pre>