public static array2Tree (array: any, parentId: number) {
        if (Tool.isEmpty(array)) {
            return [];
        }

        const result = [];
        for (let i = 0; i < array.length; i++) {
            const c = array[i];
            // console.log(Number(c.parent), Number(parentId));
            if (Number(c.parent) === Number(parentId)) {
                result.push(c);

                // 递归查看当前节点对应的子节点
                const children = Tool.array2Tree(array, c.id);
                if (Tool.isNotEmpty(children)) {
                    c.children = children;
                }
            }
        }
        return result;
    }

这里递归的过程中为什么不是先把children赋值到c变量上再push到数组？先push再赋值为什么也可以的？