按日期分类器对邮件进行排序

你的问题是与此代码：

var list = $('.messages'); 
var listItems = list.children('ul.message'); 
list.append(listItems.get().reverse()); 

此代码只接受来自.messages的UI元素，相反对它们进行排序并添加到列表的末尾，在保持日H1头列表顶部。

如果您想对日期组进行反向排序，并且还要对每组中的聊天消息进行排序，则需要稍微更改标记以包裹日期组，然后先对日期组和每组消息进行反向排序。您的标记&代码应该是这样的：

var list = $('.messages');  
var listItems = list.children('.dategroup');  
list.append(listItems.get().reverse());  
$('.dategroup').each(function(){  
    var ullist = $(this).children('ul.message')  
    $(this).append(ullist.get().reverse());  
})

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.0/jquery.min.js"></script>  
<div class="messages">  
    <div class="dategroup">  
     <h1>DATE 1</h1>  
     <ul class="message message-sent message-first message-last message-with-tail message-appear-from-bottom message-appeared"><li>chatitem 1 </li></ul>  
     <ul class="message message-sent message-first message-last message-with-tail message-appear-from-bottom message-appeared"><li>chatitem 2</li></ul>  
    </div>  
    <div class="dategroup">  
     <h1>DATE 2</h1>  
     <ul class="message message-sent message-first message-last message-with-tail message-appear-from-bottom message-appeared"><li>chatitem 3</li></ul>  
     <ul class="message message-sent message-first message-last message-with-tail message-appear-from-bottom message-appeared"><li>chatitem 4</li></ul>  
    </div>  
</div>

编辑

若要将此示例代码：

firestore.collection("chat").orderBy("date","desc").limit(10).onSnapshot(function(snapshot) {  
     $(".messages").html(''); 
     var curUser = ''; 
     var curDate = ''; 
     var curDay = ''; 
     snapshot.forEach(function(doc) { 
      console.log("djsidjsdoisjdis"); 
      $(".chat-content").animate({ scrollTop: $('.chat-content').prop("scrollHeight")}, 100); 
      if(curDate!== doc.data().date.toLocaleDateString()){ 
       curDate=doc.data().date.toLocaleDateString(); 
       var $dateGroup = $("<div class='dategroup'></div>") 
       $('.messages').append($dateGroup) 
       $dateGroup.append('<h1>'+doc.data().date.toLocaleDateString()+'</h1>'); 
      } 
      if(doc.data().user_name != username){ 
       // My message 
       if(doc.data().user_name !== curUser) { 
        // SHOW USER NAME 
        curUser = doc.data().user_name; 
        $dateGroup.append('<ul class="message message-received message-appear-from-bottom message-appeared message-first message-last message-with-tail"><li class="message-name">'+doc.data().user_name+'</li><li id="message-date" class="hide">'+doc.data().date+'</li><li class="message-text">'+doc.data().message+'</li></ul>'); 
       } else { 
        // SHOW MESSAGE WITHOUT USERNAME 
        $dateGroup.append('<ul class="message message-received message-appear-from-bottom message-appeared message-first message-last message-with-tail"><li id="message-date" class="hide">'+doc.data().date+'</li><li class="message-text">'+doc.data().message+'</li></ul>'); 
       } 
      } else { 
       // other users messages 
       if(doc.data().user_name !== curUser) { 
        // Show messsgae with user name: 
        curUser = doc.data().user_name; 
        $dateGroup.append('<ul class="message message-sent message-first message-last message-with-tail message-appear-from-bottom message-appeared"><li id="message-date" class="hide">'+doc.data().date+'</li><li class="message-name">'+doc.data().user_name+'</li><li class="message-text">'+doc.data().message+'</li></ul>'); 
       } else { 
        // Show message without user name: 
        $dateGroup.append('<ul class="message message-sent message-first message-last message-with-tail message-appear-from-bottom message-appeared"><li id="message-date" class="hide">'+doc.data().date+'</li><li class="message-text">'+doc.data().message+'</li></ul>'); 
       } 
      } 
     }); 
     var list = $('.messages'); 
     var listItems = list.children('.dategroup'); 
     list.append(listItems.get().reverse()); 
     $('.dategroup').each(function(){ 
      var ullist = $(this).children('ul.message') 
      $(this).append(ullist.get().reverse()); 
     }) 
    });