How can I get this email function to work?

The way this is written now, the email prompt opens, but when I click cancel, my default email program opens anyway. How can I re-write this to return null or false, so that when I click cancel, the default email program doesn't open?

{name: 'Email selection',
    className: 'email',
    beforeInsert: function(emailme) {
        if (emailme.altKey) {
            email = prompt("Email:");
        } else {
  开发者_高级运维          email = "";
        }
        subject = prompt("Subject:", "Enter A Subject");
        document.location = "mailto:" + email + "?subject=" + escape(subject) + "&body=" + escape(emailme.selection);
    }},

You should verify is subject is not null, and change the location only if it is not.

{name: 'Email selection',
        className: 'email',
        beforeInsert: function(emailme) {
            if (emailme.altKey) {
                email = prompt("Email:");
            } else {
                email = "";
            }
            subject = prompt("Subject:", "Enter A Subject");
            if (subject)
            {
              document.location = "mailto:" + email + "?subject=" + escape(subject) + "&body=" + escape(emailme.selection);
            }
        }},

Cover the cancel button & a blank string incase someone tries to do this to cancel.

if(subject && subject != "") {
    document.location = "mailto:" + email + "?subject=" + escape(subject) + "&body=" + escape(emailme.selection);
}

UPDATE: Example: http://blog.bmn.name/so-test