Hide Contact Form after submit

Hi,
I want to know how can i hide the contact form after submit and show the successful message.
One thing more how can i use the if,while,equals (“Conditional fields”).
for example for have one radio option and sub fields and i want show thats fields if user select the that radio option.

i had already tried the fallowing code to hide the form but not function.
<script>
document.addEventListener( ‘wpcf7mailsent’, function( event ) {
document.getElementById(‘asaphide’).style.display = ‘none’;
}, false );
</script>

Thanks and sorry for weak english