Add isArraySorted

snippets/isArraySorted.md

@@ -0,0 +1,23 @@
+### functionName
+
+Returns `1` if the 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 the first two elements.
+Use `Object.entries()` to loop over array objects and compare them in pairs.
+Return `0` if the `direction` changes or the `direction` if the last element is reached.
+
+```js
+const isArraySorted = arr => {
+  const direction = arr[0] > arr[1] ? -1 : 1;
+  for(let [i, val] of arr.entries())
+    if (i === arr.length - 1) return direction;
+    else if ((val - arr[i + 1]) * direction > 0) return 0;
+}
+```
+
+```js
+isArraySorted([0,1,2,3]) // 1
+isArraySorted([0,1,2,2]) // 1
+isArraySorted([4,3,2]) // -1
+isArraySorted([4,3,5]) // 0
+```