On line 35, why did we assign var to a parameter of a function?

function findMaxRepeatCountInWord(word) {
  
  // Break up individual words into individual letters.
  var a = word.split('');
  
  // Count the instances of each letter
  var counted = a.reduce(function(allChars,char){
    if (char in allChars) {
      allChars[char]++;
    } else {
      allChars[char] = 1;
    }
    return allChars;
  }, {});
  
  // Iterate all the counts and find the highest
  // Return this word's max repeat count
  var totals = [];
  for (var key in counted){
    totals.push(counted[key]);
  }
  return totals.reduce(function(x,y) {
    return (x > y) ? x : y;
  });
}


function findFirstWordWithMostRepeatedChars(text) {
  var maxRepeatCountOverall = 0;
  var wordWithMaxRepeatCount = '';
  text.split(" ").forEach(function(word) {
    var repeatCountForWord = findMaxRepeatCountInWord(word);
    if (repeatCountForWord > maxRepeatCountOverall) {
      maxRepeatCountOverall = repeatCountForWord;
      wordWithMaxRepeatCount = word;
    }
  });
    
      
  return wordWithMaxRepeatCount;
}

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