function rearrangeArray(arr) {
let size = arr.length;
for (let i = 1; i < size; i += 2) {
if (arr[i - 1] > arr[i]) {
[arr[i - 1], arr[i]] = [arr[i], arr[i - 1]];
}
if (i + 1 < size && arr[i + 1] > arr[i]) {
[arr[i + 1], arr[i]] = [arr[i], arr[i + 1]];
}
}
}
const arr = [1, 3, 6, 5, 4, 2, 9, 8, 7];
rearrangeArray(arr);
console.log(arr);
/*
run:
[1, 6, 3, 5, 2, 9, 4, 8, 7]
*/