SOURCE

const data = [
    {
        label: '1',
        children: [
            {
                label: '1-1',
                children: [
                    {
                        label: '1-1-1'
                    },
                    {
                        label: '1-1-2'
                    }
                ]
            },
            {
                label: '1-2',
                children: [
                    {
                        label: '1-2-1'
                    },
                    {
                        label: '1-2-2'
                    }
                ]
            }
        ]
    },
    {
        label: '1',
        children: [
            {
                label: '1-1',
                children: [
                    {
                        label: '1-1-1'
                    },
                    {
                        label: '1-1-2'
                    }
                ]
            },
            {
                label: '1-2',
                children: [
                    {
                        label: '1-2-1'
                    },
                    {
                        label: '1-2-2'
                    }
                ]
            }
        ]
    }
]
/**
 * @function 获取嵌套数据的指定层级的数据
 * @param data 嵌套数据
 * @level 获取多少层
 * @flag 当前递归到那一层
 * @return 返回指定层级的数据
 */
function getLevelData(data, level, currentLevel) {
    if (level < currentLevel) return []
    data.forEach(item => {
        // 遍历到指定层级
        let cur = currentLevel
        item.level = cur
        if (cur >= level) {
            delete item.children
        } else {
            getLevelData(item.children, level, ++cur)
        }
    })
    }
// 只需要第二个参数，输入我们想要的层级即可，返回指定层级的数据
getLevelData(data, 1, 1)
console.log(data);