数据扁平化的算法

export const serialize = (data, sections = [], weeks = []) => {
  const getWithParentArray = (newArr, parentIndex = -1, parentIndexObj = {}) =>
    newArr.map((item, index) => {
      if (item.node_lev < 2) {
        let parentObj = {};
        if (parentIndex > -1) {
          weeks[parentIndex].push(item.title);
          parentObj = { section: parentIndex, week: index };
        } else if (item.node_lev === 0) {
          sections.push(item.title);
          weeks.push([]);
        }
        return getWithParentArray(item.children, index, parentObj);
      }
      return { ...item, week: parentIndex, ...parentIndexObj };
    });
  return {
    sections,
    weeks,
    courses: getWithParentArray(data),
  };
};

export const flatten = (data, arr = []) => {
  data.forEach((item) => {
    if (item instanceof Array) {
      flatten(item, arr);
    } else {
      arr.push(item);
    }
  });
  return arr;
};

/* {
  "sections": [
    "string"
  ],
  "weeks": [
    ["string"]
  ],
  "courses": [{
    "_id": "string",
    "title": "string",
    "course_type": "NORMAL",
    "section": 0,
    "week": 0,
  }]
} */