Find Rotation Point of mostly sorted array of words

gistfile1.txt

// simple O(n), linear method

function linearFindRotationPoint(array) {
  var rotationPointIndex;
  
  for (var i = 1; i <= array.length; i++) {
    if (array[i-1] > array[i]) {
      rotationPointIndex = i;
      break;
    }
  }
  
  return rotationPointIndex;
}

console.log(linearFindRotationPoint(words))

// O(log(n)) modified binary search

function logNFindRotationPoint(array) {  
  var center = Math.floor(array.length / 2);
  var centerWord = array[center];
  var left = array[center - 1];
  var right = array[center + 1];
  
  if (centerWord < left) {
    return center;
  } else if (centerWord > right) {
    return logNFindRotationPoint(array.slice(0, center - 1));
  } else {
    return logNFindRotationPoint(array.slice(center + 1, array.length - 1));
  }
}

console.log(logNFindRotationPoint(words))