title: push() won't work as expected in reduce()
body: <p>Why doesn't <code>a.push(b)</code> work in my <code>Array.reduce()? a=a.push(b)</code> where <code>b</code> is a string, turns <code>a</code> to an integer.?!</p>
  
  <pre><code> getHighestValuesInFrequency: function(frequency) {
   //Input:var frequency = {mats: 1,john: 3,johan: 2,jacob: 3};
   //Output should become ['John','jacob']
  
  var objKeys = Object.keys(frequency);
  var highestVal = objKeys.reduce((a,b)=&gt;
              {highestVal = (frequency[b] &gt; a)? frequency[b] : a;
               return highestVal;},0);
  
  var winner = objKeys.reduce((a,b)=&gt;
        { a = (frequency[b] === highestVal)? a.push(b) : a;
          return a},[]);
  
  return winner;  
   }                                  
  </code></pre>