why is last element in the array the first value code example

Example 1: how to get first and last element of array in javascript

The rest parameter can only use at the end not anywhere else in the destructuring so it won't work as you expected.

Instead, you can destructor certain properties(an array is also an object in JS), for example, 0 for first and index of the last element for last.

let array = [1,2,3,4,5,6,7,8,9,0]

let {0 : a ,[array.length - 1] : b} = array;
console.log(a, b)
Expand snippet
Or its better way to extract length as an another variable and get last value based on that ( suggested by @Bergi) , it would work even there is no variable which refers the array.

let {0 : a ,length : l, [l - 1] : b} = [1,2,3,4,5,6,7,8,9,0];
console.log(a, b)

Example 2: last 10 element of array

System.out.print(Primes1.get(Primes1.size() - 1) + " ");