8ee50178f3
Correct: `Array.from()` (it’s a static method) Incorrect: `Array.join()` (doesn’t exist; it’s a prototype method) This patch uses the common `#` syntax to denote `.prototype.`.
24 lines
875 B
Markdown
24 lines
875 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.prototype.map()` to apply the iterator function to all elements of the array.
|
|
Use `Array.prototype.reverse()` and `Array.prototype.findIndex()` to find the appropriate last index where the element should be inserted, based on the provided iterator function.
|
|
|
|
```js
|
|
const sortedLastIndexBy = (arr, n, fn) => {
|
|
const isDescending = fn(arr[0]) > fn(arr[arr.length - 1]);
|
|
const val = fn(n);
|
|
const index = arr
|
|
.map(fn)
|
|
.reverse()
|
|
.findIndex(el => (isDescending ? val <= el : val >= el));
|
|
return index === -1 ? 0 : arr.length - index;
|
|
};
|
|
```
|
|
|
|
```js
|
|
sortedLastIndexBy([{ x: 4 }, { x: 5 }], { x: 4 }, o => o.x); // 1
|
|
```
|