jQuery.autocomplete + Fuse.js = Lighter version of mailcheck

mailcheck.lite.js

//= require fuse.min

$(function() {
  var defaultDomains = [{"host":"yahoo.com"},{"host":"google.com"},{"host":"hotmail.com"},{"host":"gmail.com"},
    {"host":"me.com"},{"host":"aol.com"},{"host":"mac.com"},{"host":"live.com"},{"host":"comcast.net"},
    {"host":"googlemail.com"},{"host":"msn.com"},{"host":"hotmail.co.uk"},{"host":"yahoo.co.uk"},{"host":"facebook.com"},
    {"host":"verizon.net"},{"host":"sbcglobal.net"},{"host":"att.net"},{"host":"gmx.com"},{"host":"mail.com"},
    {"host":"outlook.com"},{"host":"icloud.com"}];

  var fuse = new Fuse(defaultDomains, {
    caseSensitive: false,
    shouldSort: true,
    threshold: 0.6,
    location: 0,
    distance: 100,
    maxPatternLength: 32,
    keys: ["host"]
  });

  $( "input[type='email']" ).autocomplete({
    delay: 0,
    source: function(req, callback) {
      var index = req.term.indexOf("@");
      if (index == -1) return callback();
      var username = req.term.substring(0, index);
      var hostname = req.term.substring(index+1);
      var domain = null;
      var options = [];
      $.each(defaultDomains, function(index, obj) {
        if (obj.host.toLowerCase() == hostname.toLowerCase()) domain = hostname;
      });
      if (domain) {
        // exact match: don't offer autocomplete
      } else {
        $.each(fuse.search(hostname), function(index, obj) {
          domain = obj.host;
          options.push({value: [username, '@', domain].join(''), label: domain});
        });
      }
      callback(options);
    }
  }).on('blur', function(event) {
    event.target.value = event.target.value.replace(/[,]/, '.');
  });
});