Has a ton of jshint 1.0.0 RC errors (23), but none in jshint r12.

mailcheck.js

/*
 * Mailcheck https://github.com/Kicksend/mailcheck
 * Author
 * Derrick Ko (@derrickko)
 *
 * License
 * Copyright (c) 2012 Receivd, Inc.
 *
 * Licensed under the MIT License.
 *
 * v 1.1
 */

var Kicksend = {
  mailcheck : {
    threshold: 2,

    defaultDomains: ["yahoo.com", "google.com", "hotmail.com", "gmail.com", "me.com", "aol.com", "mac.com",
      "live.com", "comcast.net", "googlemail.com", "msn.com", "facebook.com", "verizon.net", "sbcglobal.net",
      "att.net", "gmx.com", "mail.com", "ymail.com", "hotmail.co.uk", "yahoo.co.uk", "live.co.uk"],

    defaultTopLevelDomains: ["co.uk", "com", "net", "org", "info", "edu", "gov", "mil"],

    whitelistRegexes: [
      /ymail.com/,
      /yahoo\.co\./,
      /yahoo\.com\./,
      /hotmail\.co\./,
      /hotmail\.com\./
    ],

    run: function (opts) {
      opts.domains = opts.domains || Kicksend.mailcheck.defaultDomains;
      opts.topLevelDomains = opts.topLevelDomains || Kicksend.mailcheck.defaultTopLevelDomains;
      opts.distanceFunction = opts.distanceFunction || Kicksend.sift3Distance;
      opts.ignoreTLDs = opts.ignoreTLDs || false;

      var result = Kicksend.mailcheck.suggest(encodeURI(opts.email), opts.domains, opts.topLevelDomains, opts.distanceFunction, opts.ignoreTLDs);

      if (result) {
        if (opts.suggested) {
          opts.suggested(result);
        }
      } else {
        if (opts.empty) {
          opts.empty();
        }
      }
    },

    suggest: function (email, domains, topLevelDomains, distanceFunction, ignoreTLDs) {
      email = email.toLowerCase();

      var emailParts = this.splitEmail(email),
        closestDomain = this.findClosestDomain(emailParts.domain, domains, distanceFunction),
        closestTopLevelDomain,
        domain,
        i,
        r;

      for (i = 0; i < this.whitelistRegexes.length; i += 1) {
        r = this.whitelistRegexes[i];
        if (r.exec(emailParts.domain)) {
          return false;
        }
      }

      if (closestDomain) {
        if (closestDomain !== emailParts.domain) {
          // The email address closely matches one of the supplied domains; return a suggestion
          return { address: emailParts.address, domain: closestDomain, full: emailParts.address + "@" + closestDomain };
        }
      } else if (!ignoreTLDs) {
        // The email address does not closely match one of the supplied domains
        closestTopLevelDomain = this.findClosestDomain(emailParts.topLevelDomain, topLevelDomains);
        if (emailParts.domain && closestTopLevelDomain && closestTopLevelDomain !== emailParts.topLevelDomain) {
          // The email address may have a mispelled top-level domain; return a suggestion
          domain = emailParts.domain;
          closestDomain = domain.substring(0, domain.lastIndexOf(emailParts.topLevelDomain)) + closestTopLevelDomain;
          return { address: emailParts.address, domain: closestDomain, full: emailParts.address + "@" + closestDomain };
        }
      }
      /* The email address exactly matches one of the supplied domains, does not closely
       * match any domain and does not appear to simply have a mispelled top-level domain,
       * or is an invalid email address; do not return a suggestion.
       */
      return false;
    },

    findClosestDomain: function (domain, domains, distanceFunction) {
      var dist,
        minDist = 99,
        closestDomain = null,
        i;

      if (!domain || !domains) {
        return false;
      }
      if (!distanceFunction) {
        distanceFunction = this.sift3Distance;
      }

      for (i = 0; i < domains.length; i += 1) {
        if (domain === domains[i]) {
          return domain;
        }
        dist = distanceFunction(domain, domains[i]);
        if (dist < minDist) {
          minDist = dist;
          closestDomain = domains[i];
        }
      }

      if (minDist <= this.threshold && closestDomain !== null) {
        return closestDomain;
      } else {
        return false;
      }
    },

    sift3Distance: function (s1, s2) {
      var c = 0,
        offset1 = 0,
        offset2 = 0,
        lcs = 0,
        maxOffset = 5,
        i;

      // sift3: http://siderite.blogspot.com/2007/04/super-fast-and-accurate-string-distance.html
      if (s1 === null || s1.length === 0) {
        if (s2 === null || s2.length === 0) {
          return 0;
        } else {
          return s2.length;
        }
      }

      if (s2 === null || s2.length === 0) {
        return s1.length;
      }

      while ((c + offset1 < s1.length) && (c + offset2 < s2.length)) {
        if (s1.charAt(c + offset1) === s2.charAt(c + offset2)) {
          lcs += 1;
        } else {
          offset1 = 0;
          offset2 = 0;
          for (i = 0; i < maxOffset; i += 1) {
            if ((c + i < s1.length) && (s1.charAt(c + i) === s2.charAt(c))) {
              offset1 = i;
              break;
            }
            if ((c + i < s2.length) && (s1.charAt(c) === s2.charAt(c + i))) {
              offset2 = i;
              break;
            }
          }
        }
        c += 1;
      }
      return (s1.length + s2.length) / 2 - lcs;
    },

    splitEmail: function (email) {
      var parts = email.split('@'),
        i,
        domain,
        domainParts,
        tld = '';

      if (parts.length < 2) {
        return false;
      }

      for (i = 0; i < parts.length; i += 1) {
        if (parts[i] === '') {
          return false;
        }
      }

      domain = parts.pop();
      domainParts = domain.split('.');

      if (domainParts.length === 0) {
        // The address does not have a top-level domain
        return false;
      } else if (domainParts.length === 1) {
        // The address has only a top-level domain (valid under RFC)
        tld = domainParts[0];
      } else {
        // The address has a domain and a top-level domain
        for (i = 1; i < domainParts.length; i += 1) {
          tld += domainParts[i] + '.';
        }
        if (domainParts.length >= 2) {
          tld = tld.substring(0, tld.length - 1);
        }
      }

      return {
        topLevelDomain: tld,
        domain: domain,
        address: parts.join('@')
      };
    }
  }
};

if (window.jQuery) {
  (function ($) {
    $.fn.mailcheck = function (opts) {
      var self = this,
        oldSuggested,
        oldEmpty;
      if (opts.suggested) {
        oldSuggested = opts.suggested;
        opts.suggested = function (result) {
          oldSuggested(self, result);
        };
      }

      if (opts.empty) {
        oldEmpty = opts.empty;
        opts.empty = function () {
          oldEmpty.call(null, self);
        };
      }

      opts.email = this.val();
      Kicksend.mailcheck.run(opts);
    };
  }(jQuery));
}