Kebab file names

snippets/sorted-index.md

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+---
+title: Insertion index in sorted array
+tags: array,math
+cover: apples
+firstSeen: 2017-12-31T16:39:06+02:00
+lastUpdated: 2020-10-22T20:24:30+03:00
+---
+
+Finds the lowest index at which a value should be inserted into an array in order to maintain its sorting order.
+
+- Loosely check if the array is sorted in descending order.
+- Use `Array.prototype.findIndex()` to find the appropriate index where the element should be inserted.
+
+```js
+const sortedIndex = (arr, n) => {
+  const isDescending = arr[0] > arr[arr.length - 1];
+  const index = arr.findIndex(el => (isDescending ? n >= el : n <= el));
+  return index === -1 ? arr.length : index;
+};
+```
+
+```js
+sortedIndex([5, 3, 2, 1], 4); // 1
+sortedIndex([30, 50], 40); // 1
+```