過濾器，地圖，排序和concat

Question

我覺得可能有更好的解決方案，因爲我在下面的例程（地圖和排序）中重複代碼。

這是一個讀取（1或null）和未讀狀態（0）的消息的任意列表。我在頂部顯示未讀消息，在底部讀取消息，並應用一些排序和映射，然後在尾部連接兩個結果。

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); 

編輯

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

好像你只是要排序多個字段。首先排序讀狀態，然後按姓氏，然後按名字（不區分大小寫），你可以：

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

爲了應對這樣的事實Read字段的null值（反直覺）被認爲是truthy，您必須引入一對臨時變量（let aRead = a.Read != null a.Read : 1）和比較這些，或改寫的比較如下：

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);

Answer 2

只動map和sort功能集成到自己的命名函數並重新使用它們：

// helpers 
function processItem(item) { 
    return {Id: item.Id, First: item.First.toLowerCase(), Last: item.Last.toLowerCase()} 
} 

function sortItemByLast(a, b) { 
    if (a.Last < b.Last) return -1; 
    if (a.Last > b.Last) return 1; 
    return 0; 
}; 

// process data 
var unread = data.filter(function(item){ 
    return item.Read == 0; 
}).map(processItem).sort(sortItemByLast); 

var read = data.filter(function(item){ 
    return item.Read == null || item.Read == 1; 
}).map(processItem).sort(sortItemByLast); 


var finalData = unread.concat(read); 

Answer 3

您可以sort，然後再使用reduce積累結果：

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} 
 
]; 
 

 
var result = data.sort(function(a, b){ 
 
    if (a.Last < b.Last) return -1; 
 
    if (a.Last > b.Last) return 1; 
 
    return 0; 
 
}).reduce(function(res, o) { 
 
    var newO = {Id: o.Id, First: o.First.toLowerCase(), Last: o.Last.toLowerCase()}; // the object to be pushed to either the read or unread array (if you are not using the old object o, then just remove the property "Read" from it and use it without creating a new object) 
 
    res[o.Read == 0? "unread": "read"].push(newO); // push o to either the read or unread array, depending on the property "Read" 
 
    return res; 
 
}, {read: [], unread: []});       // the initiale value will be an object containing two arrays (one for read and one for unread objects) 
 

 
console.log(result);