背景

在開(kāi)發(fā)過(guò)程中，對(duì)象數(shù)組的排序會(huì)經(jīng)常用到。如果想要實(shí)現(xiàn)多個(gè)字段按優(yōu)先級(jí)排序的話，如何處理？這種情況比較少見(jiàn)。舉例來(lái)說(shuō)，有以下對(duì)象數(shù)組：

const list = [
    {
        "title": "This is a deme page",
        "name": "Aborn Jiang",
        "age": 21
    },
    {
        "title": "mindpress is a good framework",
        "name": "John",
        "age": 31
    },
    {
        "title": "Goodness",
        "name": "Aborn Jiang",
        "age": 19
    }
]

如果我們想按 name 字段排序，當(dāng)name 字段相同時(shí)，再按title字段排序。
放得更加寬泛點(diǎn)，可以按任意多字段排序。

單字段排序

如果只按name排序，那調(diào)用sort方法如下：

const sortedList = list.sort((a, b) =>
     a.name.localeCompare(b.name)
)

兩字段排序

如果先按name排序，在name相同的情況下，再按 age排序，寫(xiě)法臺(tái)下：

const sortedList = list.sort((a, b) =>
     a.name.localeCompare(b.name) || a.age - b.age
)

通用多字段排序

由兩字段再擴(kuò)展到任意字段，其實(shí)是我們需要分別判斷每個(gè)字段，當(dāng)前一個(gè)字段比較后不為 0，則返回；如果為 0表示繼續(xù)采用后一個(gè)字段進(jìn)行排序，通用寫(xiě)法如下：

export interface SortFields {
  [field: string]: -1 | 1
}

export type SortOptions = SortFields

export const get = (obj: any, path: string): any => path.split('.').reduce((acc, part) => acc && acc[part], obj)

/**
 * Sort list of items by givin options
 * sort array of object by multi fields.
 * example:
 * const sortedArray = sortList(toBeSortedArray, { 'createTime': -1, 'title': 1 })
 */
export const sortList = (data: any[], params: SortOptions) => {
  const comperable = new Intl.Collator(params.$locale as string, {
    numeric: params.$numeric as boolean,
    caseFirst: params.$caseFirst as any,
    sensitivity: params.$sensitivity as any
  })
  const keys = Object.keys(params)
  data = data.sort((a, b) => {
    let res = 0;
    for (let i = 0; i < keys.length; i++) {
      const key = keys[i];
      const values = [get(a, key), get(b, key)]
        .map((value) => {
          // `null` values are treated as `"null"` strings and ordered alphabetically
          // Turn `null` values into `undefined` so they place at the end of the list
          if (value === null) {
            return undefined
          }
          // Convert Date object to ISO string
          if (value instanceof Date) {
            return value.toISOString()
          }
          return value
        })
      if (params[key as keyof SortOptions] === -1) {
        values.reverse()
      }
      res = comperable.compare(values[0], values[1])
      if (res != 0) return res;
    }
    return res;
  })
  return data
}

調(diào)用舉例：

sortedArray = sortList(toBeSortedArray, { 'createTime': -1, 'title': 1 })

先按 createTime 從最新到最舊排序（逆序，所以用-1），在時(shí)間相同的情況下，使用title排序（正序，用1）

代碼見(jiàn)： https://github.com/aborn/mindpress/blob/main/mindpress-fe/server/utils/query/sort.ts