title: how does initialValue work in javascript reduce function?
body: <p>I'm sure I'm reading this wrong but MDN says this...</p>
  
  <blockquote>
    <p><strong>initialValue</strong><br>
    Value to use as the first argument to the first call of the callback. If no initial value is supplied, the first element in the array will be used. Calling reduce() on an empty array without an initial value is an error.</p>
  </blockquote>
  
  <p><em>then</em> <em>says this</em>...Aren't these saying different things? Thanks!</p>
  
  <blockquote>
    <p>If initialValue isn't provided, reduce() will execute the callback function starting at index 1, skipping the first index. If initialValue is provided, it will start at index 0.</p>
  </blockquote>