function insertInto(array, start, newItems) {
    const startIdx = getActualStartIndex(array, start);
    const originalLength = array.length;
    const newItemsLength = newItems.length;
    array.length = originalLength + newItemsLength;
    // Move the items after the start index, start from the end so that we don't overwrite any value.
    for (let i = originalLength - 1; i >= startIdx; i--) {
        array[i + newItemsLength] = array[i];
    }
    for (let i = 0; i < newItemsLength; i++) {
        array[i + startIdx] = newItems[i];
    }
}
Insert the new items in the array.
@param array The original array.
@param start The zero-based location in the array from which to start inserting elements.
@param newItems The items to be inserted