/*

Description:

Your task is to find the first element of an array that is not consecutive.

E.g. If we have an array [1,2,3,4,6,7,8] then 1 then 2 then 3 then 4 are all consecutive but 6 is not, so that’s the first non consecutive number.

If the whole array is consecutive then return null

The array will always have at least 2 elements and all the elements will be numbers. The numbers will also all be unique and in ascending order. The numbers could be positive or negative and the first non-consecutive could be either too!

*/

function firstNonConsecutive(arr) {

const result = arr.find((number, index) => number !== index + arr[0])

return Number.isInteger(result) ? result : null

}