Validate and correct misspelled emails using a fuzzy matcher

email-test.js

/* eslint-env jasmine */

import { validate, suggest } from './email';

describe('email', () => {
  describe('validate', () => {
    it('should correctly validate correct email addresses', (done) => {
      const promises = [
        validate('[email protected]'),
        validate('[email protected]'),
        validate('[email protected]'),
        validate('[email protected]')
      ];

      Promise.all(promises).then(done, done.fail);
    });

    it('should correctly validate incorrect email addresses', (done) => {
      const promises = [
        validate('@').then(() => { throw 'fail'; }, () => true),
        validate('user [email protected]').then(() => { throw 'fail'; }, () => true),
        validate('user@domain lol.com').then(() => { throw 'fail'; }, () => true),
        validate('[email protected] om').then(() => { throw 'fail'; }, () => true),
        validate('gmail.com').then(() => { throw 'fail'; }, () => true),
        validate('@gmail.com').then(() => { throw 'fail'; }, () => true),
        validate('user@gmail.').then(() => { throw 'fail'; }, () => true),
        validate('[email protected]').then(() => { throw 'fail'; }, () => true)
      ];

      Promise.all(promises).then(done, done.fail);
    });

    it('should correctly validate an email address with unicode characters', (done) => {
      validate('snædis@💩.com').then(done, done.fail);
    });
  });

  describe('suggest', () => {
    it('should not suggest correct domains & tlds', (done) => {
      const promises = [
        suggest('[email protected]').then(e => { throw `fail: ${e}`; }, () => true),
        suggest('[email protected]').then(e => { throw `fail: ${e}`; }, () => true)
      ];

      Promise.all(promises).then(done, done.fail);
    });

    it('should not suggest correct but unknown domains & tlds', (done) => {
      const promises = [
        suggest('[email protected]').then(e => { throw `fail: ${e}`; }, () => true)
      ];

      Promise.all(promises).then(done, done.fail);
    });

    it('should not suggest emails that are too far gone', (done) => {
      const promises = [
        suggest('user@gmaillolobuzz').then(e => { throw `fail: ${e}`; }, () => true),
        suggest('[email protected]').then(e => { throw `fail: ${e}`; }, () => true)
      ];

      Promise.all(promises).then(done, done.fail);
    });

    it('should suggest misspelled domains', (done) => {
      const promises = [
        suggest('[email protected]').then(e => expect(e).toEqual('[email protected]'), () => { throw 'fail: [email protected]'; }),
        suggest('[email protected]').then(e => expect(e).toEqual('[email protected]'), () => { throw 'fail: [email protected]'; })
      ];

      Promise.all(promises).then(done, done.fail);
    });

    it('should suggest misspelled TLDs', (done) => {
      const promises = [
        suggest('[email protected]').then(e => expect(e).toEqual('[email protected]'), () => { throw 'fail: [email protected]'; }),
        suggest('[email protected]').then(e => expect(e).toEqual('[email protected]'), () => { throw 'fail: [email protected]'; }),
        suggest('[email protected]').then(e => expect(e).toEqual('[email protected]'), () => { throw 'fail: [email protected]'; }),
        suggest('[email protected]').then(e => expect(e).toEqual('[email protected]'), () => { throw 'fail: [email protected]'; })
      ];

      Promise.all(promises).then(done, done.fail);
    });

    it('should suggest misspelled TLDs for unknown domains', (done) => {
      const promises = [
        suggest('[email protected]').then(e => expect(e).toEqual('[email protected]'), () => { throw 'fail: [email protected]'; }),
        suggest('gianni@universecom').then(e => expect(e).toEqual('[email protected]'), () => { throw 'fail: gianni@universecom'; })
      ];

      Promise.all(promises).then(done, done.fail);
    });

    it('should suggest misspelled domains and TLDs', (done) => {
      const promises = [
        suggest('user@gmailcom').then(e => expect(e).toEqual('[email protected]'), () => { throw 'fail: user@gmailcom'; }),
        suggest('user@gnailcon').then(e => expect(e).toEqual('[email protected]'), () => { throw 'fail: user@gnailcon'; }),
        suggest('[email protected]').then(e => expect(e).toEqual('[email protected]'), () => { throw 'fail: [email protected]'; })
      ];

      Promise.all(promises).then(done, done.fail);
    });
  });
});

email.js

/**
 * @flow
 */

import { sift4 } from './sift';


//-----------------------------------------------------------------------------
// Misc.
//-----------------------------------------------------------------------------

export const EMAIL = /^\S+@\S+\.\S+$/u;

const DOMAINS = [
  /* Default domains included */
  'aol.com', 'att.net', 'comcast.net', 'facebook.com', 'gmail.com', 'gmx.com', 'googlemail.com',
  'google.com', 'hotmail.com', 'hotmail.co.uk', 'mac.com', 'me.com', 'mail.com', 'msn.com',
  'live.com', 'sbcglobal.net', 'verizon.net', 'yahoo.com', 'yahoo.co.uk',

  /* Other global domains */
  'email.com', 'games.com' /* AOL */, 'gmx.net', 'hush.com', 'hushmail.com', 'icloud.com', 'inbox.com',
  'lavabit.com', 'love.com' /* AOL */, 'outlook.com', 'pobox.com', 'rocketmail.com' /* Yahoo */,
  'safe-mail.net', 'wow.com' /* AOL */, 'ygm.com' /* AOL */, 'ymail.com' /* Yahoo */, 'zoho.com', 'fastmail.fm',
  'yandex.com',

  /* United States ISP domains */
  'bellsouth.net', 'charter.net', 'comcast.net', 'cox.net', 'earthlink.net', 'juno.com',

  /* British ISP domains */
  'btinternet.com', 'virginmedia.com', 'blueyonder.co.uk', 'freeserve.co.uk', 'live.co.uk',
  'ntlworld.com', 'o2.co.uk', 'orange.net', 'sky.com', 'talktalk.co.uk', 'tiscali.co.uk',
  'virgin.net', 'wanadoo.co.uk', 'bt.com',

  /* Domains used in Asia */
  'sina.com', 'qq.com', 'naver.com', 'hanmail.net', 'daum.net', 'nate.com', 'yahoo.co.jp', 'yahoo.co.kr', 'yahoo.co.id', 'yahoo.co.in', 'yahoo.com.sg', 'yahoo.com.ph',

  /* French ISP domains */
  'hotmail.fr', 'live.fr', 'laposte.net', 'yahoo.fr', 'wanadoo.fr', 'orange.fr', 'gmx.fr', 'sfr.fr', 'neuf.fr', 'free.fr',

  /* German ISP domains */
  'gmx.de', 'hotmail.de', 'live.de', 'online.de', 't-online.de' /* T-Mobile */, 'web.de', 'yahoo.de',

  /* Russian ISP domains */
  'mail.ru', 'rambler.ru', 'yandex.ru', 'ya.ru', 'list.ru',

  /* Belgian ISP domains */
  'hotmail.be', 'live.be', 'skynet.be', 'voo.be', 'tvcablenet.be', 'telenet.be',

  /* Argentinian ISP domains */
  'hotmail.com.ar', 'live.com.ar', 'yahoo.com.ar', 'fibertel.com.ar', 'speedy.com.ar', 'arnet.com.ar',

  /* Domains used in Mexico */
  'hotmail.com', 'gmail.com', 'yahoo.com.mx', 'live.com.mx', 'yahoo.com', 'hotmail.es', 'live.com', 'hotmail.com.mx', 'prodigy.net.mx', 'msn.com',

  /* Domains used in Brazil */
  'yahoo.com.br', 'hotmail.com.br', 'outlook.com.br', 'uol.com.br', 'bol.com.br', 'terra.com.br', 'ig.com.br', 'itelefonica.com.br', 'r7.com', 'zipmail.com.br', 'globo.com', 'globomail.com', 'oi.com.br'
];

const HOSTS = [
  'aim', 'aol', 'att', 'bellsouth', 'btinternet', 'charter', 'comcast', 'cox',
  'earthlink', 'gmail', 'google', 'googlemail', 'icloud', 'mac', 'me', 'msn',
  'optonline', 'optusnet', 'qq', 'rocketmail', 'rogers', 'sbcglobal', 'shaw',
  'sky', 'sympatico', 'telus', 'verizon', 'web', 'xtra', 'ymail'
];

const TLDS = [
  'com', 'com.au', 'com.tw', 'ca', 'co.nz', 'co.uk', 'de', 'fr', 'it', 'ru',
  'net', 'org', 'edu', 'gov', 'jp', 'nl', 'kr', 'se', 'eu', 'ie', 'co.il',
  'us', 'at', 'be', 'dk', 'hk', 'es', 'gr', 'ch', 'no', 'cz', 'in', 'net',
  'net.au', 'info', 'biz', 'mil', 'co.jp', 'sg', 'hu', 'uk'
];


//-----------------------------------------------------------------------------
// Validate
//-----------------------------------------------------------------------------

export function validate(email: string): Promise<void> {
  if (!EMAIL.test(email)) {
    return Promise.reject();
  }

  return Promise.resolve();
}


//-----------------------------------------------------------------------------
// Suggest
//-----------------------------------------------------------------------------

type Match = {
  distance: number;
  match: string;
};

function findClosest(haystack: Array<string>, needle: string, threshold: number = 2): ?Match {
  const closest: ?Match = haystack.reduce((prev: ?Match, d: string) => {
    const distance = sift4(needle, d, 5, 13);
    const current: Match = {
      distance,
      match: d
    };

    if (!prev) {
      return current;
    }

    return (current.distance < prev.distance) ? current : prev;
  }, undefined);

  if (closest && closest.distance > threshold) {
    return undefined;
  }

  return closest;
}

export function suggest(email: string): Promise<string> {
  const match = /(\S+?@)(\S+?(\.\S{2,}|\S{3})?)$/u.exec(email);

  if (!match) {
    return Promise.reject();
  }

  const [, user, domain, tld] = match;

  // Check full domain
  if (DOMAINS.includes(domain)) {
    return Promise.reject();
  }

  const closestDomain = findClosest(DOMAINS, domain);

  if (closestDomain) {
    return Promise.resolve(`${user}${closestDomain.match}`);
  }

  // Check host and top-level domains
  if (tld) {
    const host = domain.slice(0, (-1 * tld.length));
    const closestHost = findClosest(HOSTS, host);
    const strippedTld = (tld[0] === '.')
      ? tld.slice(1)
      : tld;
    const threshold = (domain.indexOf('.') >= 0) ? 2 : 1;
    const closestTld = findClosest(TLDS, strippedTld, threshold);

    if (!closestHost) {
      if (!closestTld) {
        return Promise.reject();
      }

      let suggest = `${user}${host}.${closestTld.match}`;

      if (suggest === email) {
        return Promise.reject();
      }

      return Promise.resolve(suggest);
    }
    else if (!closestTld || ((closestHost.distance === 0) && (closestTld.distance === 0))) {
      return Promise.reject();
    }

    return Promise.resolve(`${user}${closestHost.match}.${closestTld.match}`);
  }

  return Promise.reject();
}

sift.js

/* eslint-disable */
// Sift4 - common version
// online algorithm to compute the distance between two strings in O(n)
// maxOffset is the number of characters to search for matching letters
// maxDistance is the distance at which the algorithm should stop computing the value and just exit (the strings are too different anyway)
export function sift4(s1, s2, maxOffset, maxDistance) {
  if (!s1 || !s1.length) {
    if (!s2) {
      return 0;
    }
    return s2.length;
  }

  if (!s2 || !s2.length) {
    return s1.length;
  }

  var l1 = s1.length;
  var l2 = s2.length;

  var c1 = 0; //cursor for string 1
  var c2 = 0; //cursor for string 2
  var lcss = 0; //largest common subsequence
  var local_cs = 0; //local common substring
  var trans = 0; //number of transpositions ('ab' vs 'ba')
  var offset_arr = []; //offset pair array, for computing the transpositions

  while ((c1 < l1) && (c2 < l2)) {
    if (s1.charAt(c1) == s2.charAt(c2)) {
      local_cs++;
      var isTrans = false;
      //see if current match is a transposition
      var i = 0;
      while (i < offset_arr.length) {
        var ofs = offset_arr[i];
        if (c1 <= ofs.c1 || c2 <= ofs.c2) {
          // when two matches cross, the one considered a transposition is the one with the largest difference in offsets
          isTrans = Math.abs(c2 - c1) >= Math.abs(ofs.c2 - ofs.c1);
          if (isTrans) {
            trans++;
          } else {
            if (!ofs.trans) {
              ofs.trans = true;
              trans++;
            }
          }
          break;
        } else {
          if (c1 > ofs.c2 && c2 > ofs.c1) {
            offset_arr.splice(i, 1);
          } else {
            i++;
          }
        }
      }
      offset_arr.push({
        c1: c1,
        c2: c2,
        trans: isTrans
      });
    } else {
      lcss += local_cs;
      local_cs = 0;
      if (c1 != c2) {
        c1 = c2 = Math.min(c1, c2); //using min allows the computation of transpositions
      }
      //if matching characters are found, remove 1 from both cursors (they get incremented at the end of the loop)
      //so that we can have only one code block handling matches 
      for (var i = 0; i < maxOffset && (c1 + i < l1 || c2 + i < l2); i++) {
        if ((c1 + i < l1) && (s1.charAt(c1 + i) == s2.charAt(c2))) {
          c1 += i - 1;
          c2--;
          break;
        }
        if ((c2 + i < l2) && (s1.charAt(c1) == s2.charAt(c2 + i))) {
          c1--;
          c2 += i - 1;
          break;
        }
      }
    }
    c1++;
    c2++;
    if (maxDistance) {
      var temporaryDistance = Math.max(c1, c2) - lcss + trans;
      if (temporaryDistance >= maxDistance) return Math.round(temporaryDistance);
    }
    // this covers the case where the last match is on the last token in list, so that it can compute transpositions correctly
    if ((c1 >= l1) || (c2 >= l2)) {
      lcss += local_cs;
      local_cs = 0;
      c1 = c2 = Math.min(c1, c2);
    }
  }
  lcss += local_cs;
  return Math.round(Math.max(l1, l2) - lcss + trans); //add the cost of transpositions to the final result
}
/* eslint-enable */