javascript - 过滤、映射、排序和连接

Question

我觉得可能有更好的解决方案，因为我在以下例程(映射和排序)中有重复代码。

它是具有已读(1 或 null)和未读状态 (0) 的任意消息列表。我在顶部显示未读消息，在底部显示已读消息，并应用了一些排序和映射，然后在最后连接两个结果。

var unread = data.filter(function(item){
    return item.Read == 0;
}).map(function(item){
    return {Id: item.Id, First: item.First.toLowerCase(), Last: item.Last.toLowerCase()}
}).sort(function(a, b){
    if (a.Last < b.Last) return -1;
    if (a.Last > b.Last) return 1;
    return 0;
});

var read = data.filter(function(item){
    return item.Read == null || item.Read == 1;
}).map(function(item){ // lowercase (first, last) and sort the list by last
    return {Id: item.Id, First: item.First.toLowerCase(), Last: item.Last.toLowerCase()}
}).sort(function(a, b){
    if (a.Last < b.Last) return -1;
    if (a.Last > b.Last) return 1;
    return 0;
});

var finalData = unread.concat(read);

编辑

var input = [
    {Id: 1, First: "John", Last: "B", Read:0},
    {Id: 1, First: "Jane", Last: "C", Read:0},
    {Id: 1, First: "Doe", Last: "D", Read:1},
    {Id: 1, First: "Alpha", Last: "B", Read:1},
    {Id: 1, First: "Beta", Last: "C", Read:null},
    ];

var output = [
    {Id: 1, First: "Alpha", Last: "B", Read:1},
    {Id: 1, First: "Doe", Last: "D", Read:1},
    {Id: 1, First: "Beta", Last: "C", Read: null},
    {Id: 1, First: "John", Last: "B", Read:0}
    {Id: 1, First: "Jane", Last: "C", Read:0},
];

Answer 1

您似乎只想对多个字段进行排序。要先按阅读状态排序，然后按姓氏排序，然后按名字排序(忽略大小写)，您可以:

var data = [
  {Id: 1, First: "John", Last: "B", Read:0},
  {Id: 1, First: "Jane", Last: "C", Read:0},
  {Id: 1, First: "Doe", Last: "D", Read:1},
  {Id: 1, First: "Alpha", Last: "B", Read:1}
];

data.sort((a, b) =>
  b.Read !== a.Read
    ? b.Read - a.Read
    : a.Last.toLowerCase().localeCompare(b.Last.toLowerCase())
      ? a.Last.toLowerCase().localeCompare(b.Last.toLowerCase())
      : a.First.toLowerCase().localeCompare(b.First.toLowerCase()));
    
console.log(data);

更新

要处理 Read 字段的 null 值(违反直觉)被认为是 truthy 这一事实，您必须引入几个临时变量(let aRead = a.Read != null a.Read : 1)并比较它们，或者重写比较如下:

var data = [
  {Id: 1, First: "John", Last: "B", Read:0},
  {Id: 1, First: "Jane", Last: "C", Read:0},
  {Id: 1, First: "Doe", Last: "D", Read:1},
  {Id: 1, First: "Alpha", Last: "B", Read:1},
  {Id: 1, First: "Beta", Last: "C", Read:null}
];

data.sort((a, b) =>
  b.Read !== a.Read
    ? (b.Read != null ? b.Read : 1) - (a.Read != null ? a.Read : 1)
    : a.Last.toLowerCase().localeCompare(b.Last.toLowerCase())
      ? a.Last.toLowerCase().localeCompare(b.Last.toLowerCase())
      : a.First.toLowerCase().localeCompare(b.First.toLowerCase()));
    
console.log(data);