Best algorithm to perform alternate sorting of array using javascript?

Question

The following was my interview question. But I couldn't crack it and even could not think how to get this done.

var arr = [1,4,5,8,3,2,6,9,7,10];

Expected output of alternate sorting:

[10,1,9,2,8,3,7,4,6,5]

What I have tried:
I tried slicing out the Math.max.apply(null,arr) and Math.min.apply(null,arr) alternatively to push into separate empty array. But It was told that the algorithm is not optimal.

Answer 1

I would sort the array, and then iterate it, picking values from the begining and the end (inloop calculated offsets), in each iteration. A final check to odd arrays would complete the process.

let a = [1, 4, 5, 8, 3, 2, 6, 9, 7, 10];
a.sort((a, b) => a - b);
let b =[];
    
let l = a.length-1;  // micro optimization
let L = l/2;         // micro optimization
for(var i=0; i<L; i++) b.push( a[l-i] ,a[i] );
if(a.length%2) b.push( a[i] ); // add last item in odd arrays

console.log(b);

Result :

b =  [10, 1, 9, 2, 8, 3, 7, 4, 6, 5]

Algorithm bennefits:

• Avoiding alterations in the original array (through pop and shift), improves the performance considerably.
• Precalculating l and L before the loop , prevents the need of being calculated repeatedly in each iteration.
• A single conditional cheking at the end of the procces, to handle odd arrays, slightly improves the speed.

I've prepared some PERFORMANCE TESTS, with some of the proposed algorithms : Original Array(10 items) and Big Array(1000 items)