23 lines
797 B
Markdown
23 lines
797 B
Markdown
### sortedLastIndexBy
|
|
|
|
Returns the highest index at which value should be inserted into array in order to maintain its sort order, based on a provided iterator function.
|
|
|
|
Check if the array is sorted in descending order (loosely).
|
|
Use `Array.reverse()` and `Array.findIndex()` to find the appropriate last index where the element should be inserted, based on the iterator function `fn`..
|
|
|
|
```js
|
|
const sortedLastIndexBy = (arr, n, fn) => {
|
|
const isDescending = fn(arr[0]) > fn(arr[arr.length - 1]);
|
|
const val = fn(n);
|
|
const index = arr
|
|
.map((val, i) => [i, fn(val)])
|
|
.reverse()
|
|
.findIndex(el => (isDescending ? val <= el[1] : val >= el[1]));
|
|
return index === -1 ? 0 : arr.length - index;
|
|
};
|
|
```
|
|
|
|
```js
|
|
sortedLastIndexBy([{ 'x': 4 }, { 'x': 5 }], { 'x': 4 }, o => o.x); // 1
|
|
```
|