How to hide flash message after few seconds?

You can try :

setTimeout(function() {
    $('#successMessage').fadeOut('fast');
}, 30000); // <-- time in milliseconds

If you used this then your div will be hide after 30 sec.I also tried this one and it worked for me.

You can use the delay jQuery API to achieve this.

$(document).ready(function(){
    $("#successMessage").delay(5000).slideUp(300);
});

Someone posted a similar question to stackoverflow with this solution:

<script type="text/javascript">window.setTimeout("document.getElementById('successMessage').style.display='none';", 2000); </script>

<div id="successMessage"> bla bla bla
</div>

I'd share the link but I can't find it anymore. Thanks for the help, though, mystery human!