const example = (arr) => {
    let result = [];
    if (Array.prototype.hasOwnProperty.call(arr, 0) && arr[0] instanceof Object)
        result.push(arr[0]);
    let lastObj = result[0];
    for (let i = 1; i < arr.length; ++i) {
        const el = arr[i];
        if (el && el instanceof Object) {
            lastObj.children = el;
            lastObj = el;
        }
    }
    return result;
}