How to find missing element?

Question

JavaScript

Hello.
The essence of the task is to find a pass. number.
For example - Prompt algorithm please. const arr = [2, 5, 1, 4, 9, 6, 3, 7]
missingNum(arr) // => 8

Answer 1

You can sort, and during this check the difference of a smaller number over a larger one, if the result is greater than one, a number is missing between them, find it, add +1 to the smaller one or -1 from the larger one