function soundex(word) {

    // first make it all uppercase

    var treatedWord = word.toUpperCase(); // 'PHARRELL'

​

    // Take first letter as our hash prefix

    var hash = treatedWord[0];  // 'P'

    // step 2. Replace consonants with digits

    var lettersToReplaceInOrder = ['BFPV', 'CGJKQSXZ', 'DT', 'L', 'MN', 'R', 'WH', 'AEIOUY'];

    lettersToReplaceInOrder.forEach(function(lettersToReplace, index) {

        treatedWord = treatedWord.replace(new RegExp("["+ lettersToReplace +"]",'gi'), index + 1);

    });  // treatedWord = '7866844'

​

    // update our has

    hash += treatedWord;  // 'P7866844'

​

    // now we have to remove duplicate numbers

    // we split the string into an array and run it through a map function

    // the map funtction

    hash = hash.split("")

      .map(function(number, index, array) {

        // if it's not the first letter 

        //     AND the previous character is a vowel 

        //     AND the previous previous character is the same as the current 

        if (index > 1 && (array[index - 1] === '7' && array[index - 2] === number)) {

          // do nothing... this counts as two identical characters next to each other

        } 

        // else if this is the first character

        //     OR the previous character did not match this character

        else if (index === 0 || (array[index - 1] !== number)) {

          // then return it

          return number;

        }

      }).join("");  // hash = 'P78684'

​

      // ALMOST THERE!

      // Now we just need drop out vowels, non word characters and trim to 4 or less

      hash = hash[0] + hash.substring(1).replace(/[78\W]/gi, ""); // 'P64'

      hash = hash.substring(0, 4).trim();

     // Now we have to make sure the length is 4

     // if not then pad it with 0

     while (hash.length < 4) {

         hash += '0';

     }

​

     return hash; // 'P640'

}

​

function runSearch() {

  var artists = document.getElementById('artists').value.split(', ');

  // build up map of soundex to artist

  var artistMap = artists.reduce(function(obj, artist) {

    var key = soundex(artist);

    if (!obj[key]) {

      obj[key] = [artist];

    } else {

      obj[key].push(artist);      

    }

    return obj;

  }, {});

  // get soundex for our search string

  var searchQuery = document.getElementById('search-query').value;

  var soundexHash = soundex(searchQuery);

  // display results

  if (artistMap[soundexHash]) {

    document.getElementById('search-results').innerText = artistMap[soundexHash].join(', ');

  } else {

    document.getElementById('search-results').innerText = 'No matches found :(';

  }

}

​