25 lines
759 B
Markdown
25 lines
759 B
Markdown
---
|
|
title: sortedIndexBy
|
|
tags: array,math,intermediate
|
|
---
|
|
|
|
Finds the lowest index at which a value should be inserted into an array in order to maintain its sorting order, based on the provided iterator function.
|
|
|
|
- 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, based on the iterator function `fn`.
|
|
|
|
```js
|
|
const sortedIndexBy = (arr, n, fn) => {
|
|
const isDescending = fn(arr[0]) > fn(arr[arr.length - 1]);
|
|
const val = fn(n);
|
|
const index = arr.findIndex(el =>
|
|
isDescending ? val >= fn(el) : val <= fn(el)
|
|
);
|
|
return index === -1 ? arr.length : index;
|
|
};
|
|
```
|
|
|
|
```js
|
|
sortedIndexBy([{ x: 4 }, { x: 5 }], { x: 4 }, o => o.x); // 0
|
|
```
|