[рони]

function insertsInPlace(arr, value) {
            const len = arr.length;
            for (let i = len - 1, k = 2 * i; i >= 0; --i, k -= 2) {
                arr[k] = arr[i];
                arr[k + 1] = value;
            }
            return arr;
        }

        const arr = [2, 3, 4, 5];
        insertsInPlace(arr, 1);
        alert(JSON.stringify(arr));