JavaScript递归树形扁平数组笔试题reduceforEachconcat

Posted 2022-05-24 web半晨

目录

• 1、数据源
• • 1.1、扁平数组
  • 1.2、JSON树形
• 2、题目
• • 2.1、题目一
  • 2.2、题目二
  • 2.3、题目三
  • 2.4、题目四
  • 2.5、题目五

---

1、数据源

1.1、扁平数组

let flatOriginData = [
     id: 5, parentId: 2, name: "目录1-1-1", ,
     id: 1, parentId: 0, name: "目录1", ,
     id: 13, parentId: 9, name: "目录2-2-3", ,
     id: 3, parentId: 1, name: "目录1-2", ,
     id: 2, parentId: 1, name: "目录1-1", ,
     id: 12, parentId: 9, name: "目录2-2-2", ,
     id: 4, parentId: 1, name: "目录1-3", ,
     id: 7, parentId: 0, name: "目录2", ,
     id: 9, parentId: 7, name: "目录2-2", ,
     id: 6, parentId: 2, name: "目录1-1-2", ,
     id: 11, parentId: 9, name: "目录2-2-1", ,
     id: 8, parentId: 7, name: "目录2-1", ,
     id: 10, parentId: 7, name: "目录2-3", ,
];

---

1.2、JSON树形

let treeOriginData = [
    
        id: 1, parentId: 0, name: "目录1",
        children: [
             id: 3, parentId: 1, name: "目录1-2" ,
            
                id: 2, parentId: 1, name: "目录1-1",
                children: [
                     id: 5, parentId: 2, name: "目录1-1-1" ,
                     id: 6, parentId: 2, name: "目录1-1-2" 
                ]
            ,
             id: 4, parentId: 1, name: "目录1-3" 
        ]
    ,
    
        id: 7, parentId: 0, name: "目录2",
        children: [
            
                id: 9, parentId: 7, name: "目录2-2",
                children: [
                     id: 13, parentId: 9, name: "目录2-2-3" ,
                     id: 12, parentId: 9, name: "目录2-2-2" ,
                     id: 11, parentId: 9, name: "目录2-2-1" 
                ]
            ,
             id: 8, parentId: 7, name: "目录2-1" ,
             id: 10, parentId: 7, name: "目录2-3" 
        ]
    
];

---

2、题目

2.1、题目一

通过代码不全实现扁平数组结构转成JSON树形结构。parentId属性记录的是父级id值。

---

function convert(list) 
    // 补全代码
	let map = ,
        result = [];

        list.forEach(item => map[item.id] = item);

        list.forEach(item => 
            let parent = map[item.parentId];

            if (parent) 
                parent.children = parent.children || [];
                parent.children.push(item);
             else 
                result.push(item);
            
        );

        return result;


// 输出结果
console.log('convert:', convert(flatOriginData));

---

2.2、题目二

1、给树形的每一项添加age属性/字段，age属性值为1~10的随机数。
2、把数字类型的parentId属性的值改为字符串类型。

---

function treeRecursion(data) 
    // 补全代码
	for (const key in data) 
    	if (Object.hasOwnProperty.call(data, key)) 
            let item = data[key];

            if (key === 'id') (data['age'] = Math.round(Math.random() * 10), data.parentId = data.parentId.toString());

            if (typeof item === 'object') treeRecursion(item);
        
    

    return data;


// 输出结果
console.log('treeRecursion:', treeRecursion(treeOriginData));

---

2.3、题目三

通过代码补全实现JSON树形结构转成扁平数组结构，每一项数据不能出现多余的children子项。

---

function flatten(arr) 
    // 补全代码
	return arr.reduce((par, cur) => 
    	let  id, name, parentId, children = []  = cur;
        return par.concat([ id, name, parentId ], children.length ? flatten(children) : []);
    , []);


// 输出结果
console.log('flatten:', flatten(treeOriginData));

---

2.4、题目四

根据id获取树形对应数据项，也就是根据id进行数据查找、搜索、查询，找不到返回undefined。

---

function findItemById(list, id) 
	// 补全代码
	let res = list.find(item => item.id === id),
        result = undefined;

    if (!res) 
        list.forEach(item => 
            res = findItemById(item.children ? item.children : [], id);

            if (res) (delete res.children, result = res);

        );
     else 
        delete res.children;
        result = res;
    

    return result;


// 输出结构
console.log('findItemById:', findItemById(treeOriginData, 10));

---

2.5、题目五

根据子级id获取父级id，直至顶级id为止。

---

function funRecursion(list, id) 
    // 补全代码
	for (const key in list) 
		if (Object.hasOwnProperty.call(list, key)) 
			if (list[key].id === id) return [list[key].id];
			let res = funRecursion(list[key].children ? list[key].children : [], id);
			if (res) return res.concat([list[key].id]);
		
	
;

// 输出结果/原始输出
console.log(funRecursion(treeOriginData, 5));