o2e.js

let arra = [1, 4, 5, 6, 7]

var duplicate = []
let o = []
let e = []
var on = 0;
var en = 0;

console.log("original array ", arra)

const o2e = (arr) => {

    for (let i = 0; i < arr.length; i += 2) {
        o.push(arr[i])
    }
    for (let i = 1; i < arr.length; i += 2) {
        e.push(arr[i])
    }

    for (let jo = 0; jo < arr.length; jo++) {
        switch (jo % 2 == 0) {
            case true:
                for (let i = 0; i < o.length; i++) {
                    duplicate.push(e[en])
                    break
                }
                en++
                break
            case false:
                for (let i = 0; i < e.length; i++) {
                    duplicate.push(o[on])
                    break;
                }
                on++
                break

            default:
        }
    }

    console.log(duplicate)
}

if (arra.length % 2 == 0) {
    o2e(arra)
}
else {
    var pos = Math.floor(arra.length / 2)
    arra.splice(pos, 1)

    o2e(arra)
}