mostFrequentJS created by dtstanley - https://repl.it/FfGw/116

mostFrequentJS.js

function getTokens(rawString) {
  // NB: `.filter(Boolean)` removes any falsy items from an array
  return rawString.toLowerCase().split(/[ ,!.";:-]+/).filter(Boolean).sort();
}
//This function counts the number of times each word appears in the text (colletion)
function mostFrequentWord(text) {
  //the getTokens function is invoked and the results are saved as the variable words
  var words = getTokens(text);
  //the wordFrequencies array is created
  var wordFrequencies = {};
  //each word in the wordFrequencies array is identified and counted
  for (var i = 0; i <= words.length; i++) {
    if (words[i] in wordFrequencies) {
      wordFrequencies[words[i]]++;
    }
    else {
  //if a word is only found once, it is identified as such
      wordFrequencies[words[i]]=1;
    }
  }
  //the currentMaxKey variable is defined and initiated with the first key in the array
  var currentMaxKey = Object.keys(wordFrequencies)[0];
  //the currentMaxCount variable is defined and initiated with the first value, of the first key, in the array
  var currentMaxCount = wordFrequencies[currentMaxKey];
  //the loop identifies which word has the highest count and what the count is
  for (var word in wordFrequencies) {
    //the currentMaxCount is compared with the count for each word in the array
    //if the count for the word is greater than the currentMaxCount, 
    // then the word becomes the new currentMaxKey
    if (wordFrequencies[word] > currentMaxCount) {
      currentMaxKey = word;
      //and the word's count replaces the currentMaxCount
      currentMaxCount = wordFrequencies[word];
    }
  }
  //the word with the highest number count is returned to the invoking call
  return currentMaxKey;
}

var spaceOddityText = 'Ground Control to Major Tom\n \
        Ground Control to Major Tom\n \
        Take your protein pills and put your helmet on\n \
        Ground Control to Major Tom (ten, nine, eight, seven, six)\n \
        Commencing countdown, engines on (five, four, three)\n \
        Check ignition and may God\'s love be with you (two, one, liftoff)\n \
        \n \
        This is Ground Control to Major Tom\n \
        You\'ve really made the grade\n \
        And the papers want to know whose shirts you wear\n \
        Now it\'s time to leave the capsule if you dare\n \
        "This is Major Tom to Ground Control\n \
        I\'m stepping through the door\n \
        And I\'m floating in a most peculiar way\n \
        And the stars look very different today\n \
        For here\n \
        Am I sitting in a tin can\n \
        Far above the world\n \
        Planet Earth is blue\n \
        And there\'s nothing I can do\n \
        \n \
        Though I\'m past one hundred thousand miles\n \
        I\'m feeling very still\n \
        And I think my spaceship knows which way to go\n \
        Tell my wife I love her very much she knows\n \
        Ground Control to Major Tom\n \
        Your circuit\'s dead, there\'s something wrong\n \
        Can you hear me, Major Tom?\n \
        Can you hear me, Major Tom?\n \
        Can you hear me, Major Tom?\n \
        Can you \"Here am I floating \'round my tin can\n \
        Far above the moon\n \
        Planet Earth is blue\n \
        And there\'s nothing I can do\"';
        
var rawStringLowerCased =  'ground control to major tim \n \
         ground control to major tim\n \
         take your protein pills and put your helmet on\n \
         ground control to major tim (ten, nine, eight, seven, six)\n \
         commencing countdown, engines on (five, four, three)\n \
         check ignition and may god\'s love be with you (two, one, liftoff)\n \
         \n \
         this is ground control to major tom\n \
         you\'ve really made the grade\n \
         and the papers want to know whose shirts you wear\n \
         now it\'s time to leave the capsule if you dare\n \
         "this is major tom to ground control\n \
         i\'m stepping through the door\n \
         and i\'m floating in a most peculiar way\n \
         and the stars look very different today\n \
         for here\n \
         am i sitting in a tin can\n \
         far above the world\n \
         planet earth is blue\n \
         and there\'s nothing i can do\n \
         \n \
         though i\'m past one hundred thousand miles\n \
         i\'m feeling very still\n \
         and i think my spaceship knows which way to go\n \
         tell my wife i love her very much she knows\n \
         ground control to captain tom\n \
         your circuit\'s dead, there\'s something wrong\n \
         can you hear me, captain tom?\n \
         can you hear me, captain tom?\n \
         can you hear me, captain tom?\n \
         can you \"here am i floating \'round my tin can\n \
         far above the moon\n \
         planet earth is blue\n \
         and there\'s nothing i can do\" ';       

mostFrequentWord(spaceOddityText) + '\' and also \'' + mostFrequentWord(rawStringLowerCased);