Red. email availability button and database connectivity

Question

hello,

I am making a project on email management system for an organisation.I want to add check availability button in my registration form. when user will click on this button than it should check that whether the email id which user has selected exist in database or not.If it exist than it should print unavailable next to the button without refreshing page and if not exist than it should print available next to the button.we can only use jsp,servlets ,html or javascript for this.please help me because i am stuck on this thing due to which not able to complete project.