关于前端:关于递归-整理

对于递归，算法当中根底中的根底，把握不好，所有算法都是0.
以下是几个递归，在了解当中记忆，记录它们重在了解，不在记忆。

1、多维数组打成map映射。

const buildMapDataSource = (  dataSource,  target = {},  level = 1,  parentKey = null,) => {  for (let i = 0; i < dataSource.length; i++) {    const item = dataSource[i];    let key = !parentKey ? `${i}` : `${parentKey}-${i}`;    if (!target[item.id]) {      target[item.id] = item;      item.level = level;      item.key = key;    }    if (Array.isArray(item?.children)) {      buildMapDataSource(item.children, target, level + 1, key);    }  }  return target;};

2、多维数组，每项打入key，示意层级，相似key='0-0-0-1'.

const buildStandardArr = (data, parentId = null) => {  const result = [];  data.forEach((item, index) => {    if (item.parentId === parentId) {      const key = parentId !== null ? `${parentId}-${index}` : `${index}`;      const newItem = { ...item, key };      const children = buildStandardArr(data, item.id);      if (Array.isArray(children) && children.length) {        newItem.children = children;      }      result.push(newItem);    }  });  return result;}

3、把一维打成tree多维，集体感觉这个比拟难了解；

const buildMultipleArr = (data, parentId = null) => {  const result = [];  data.forEach(item => {    if (item.parentId === parentId) {      const children = buildMultipleArr(data, item.id);      const newItem = { ...item };      if (Array.isArray(children) && children.length) {        newItem.children = children;      }      result.push(newItem);    }  });  return result;};

4、通过parentId获取parent

const getParent = (data, parentId = null, parent = null) => {  for (let i = 0; i < data.length; i++) {    const item = data[i];    if (item.parentId === parentId) {      return parent;    }    if (Array.isArray(item?.children) && item.children.length) {      const parent = getParent(item.children, parentId, item);      if (parent) {        return parent;      }    }  }  return null;}

5、对多维数组，外部的节点排序

const sortNodes = (data) => {  data.sort((a, b) => a.sort - b.sort)  data.forEach(item => {    if (Array.isArray(item?.children) && item.children.length) {      sortNodes(item.children);    }  });  return data;}

6、获取多维数组，某一项Item外部（有多层children嵌套）最大的层级

const getMaxLevel = (obj) => {  let maxLevel = 0;  function traverse(node, level) {    if (level > maxLevel) {      maxLevel = level;    }    if (Array.isArray(node.children)) {      node.children.forEach(child => {        traverse(child, child.level);      });    }  }  traverse(obj, obj.level);  return maxLevel;}

从下面的例子来看
须要数组push的，都是先写递归函数，再写push追加的内容
须要返回一个object的，都是先写逻辑，再写递归函数