Update isSorted.md

snippets/isSorted.md

@@ -3,17 +3,18 @@ title: isSorted
 tags: array,intermediate
 ---
 
-Returns `1` if an array of numbers is sorted in ascending order, `-1` if it is sorted in descending order or `0` if it is not sorted.
+Returns `1` if a numeric array is sorted in ascending order, `-1` if it is sorted in descending order or `0` if it is not sorted.
 
-- Calculate the ordering `direction` for every pair of adjacent array elements.
-- Return `0` if the `direction` changes or the `direction` sign if the last element is reached.
+- Calculate the ordering `direction` for the first pair of adjacent array elements.
+- Return `0` if the given array is empty, only has one element or the `direction` changes for any pair of adjacent array elements.
+- Use `Math.sign()` to covert the final value of `direction` to `-1` or `1`.
 
 ```js
 const isSorted = arr => {
-  let direction = 0;
-  for (let i = 1; i < arr.length; i++) {
-    if (!direction) direction = arr[i] - arr[i - 1];
-    else if ((arr[i] - arr[i - 1]) * direction < 0) return 0;
+  if (arr.length <= 1) return 0;
+  const direction = arr[1] - arr[0];
+  for (let i = 2; i < arr.length; i++) {
+    if ((arr[i] - arr[i - 1]) * direction < 0) return 0;
   }
   return Math.sign(direction);
 };