Is there any javascript ssh client?

Not in JavaScript that I know off, but you can run a python script on the server that will provide you with an ssh-shell in a browser.

GateOne

Not pure HTML5, but there are other online (html/js/css based)

• Firessh
• Webshell (no longer resolves as of 06/2016)
• sshterm (no longer resolves as of 06/2016)