findPeakRecursive

// Given an array of integers, find a peak if it exists
// Where a peak is defined as greater than or equal to previous 
// and subsequent values (for edge, >= to sole neighbor)

var isPeak = function(l,m,r) {
  if (typeof l === 'undefined') {
    return (m>=r)
  } else if (typeof r === 'undefined') {
    return (m>=l);
  } else {
    return ((m >= l) && (m >= r));
  }
}

var findPeakRecurs = function(array, position = Math.floor(array.length/2)) {
  
  var mid = array[position];
  var left = array[position - 1];
  var right = array[position + 1];
  
  if (isPeak(left, mid, right)) {
    return position;
  } else if (left > mid) {
    // So look at the mid of the left side
    return findPeakRecurs(array, Math.floor(position/2))
  } else {
    // So look at the mid of the right side
    return findPeakRecurs(array, Math.floor(position + (array.length - position)/2))
  }
  
}