对象的排序列表反应-本机按值而不是键。

Question

我在对React中的对象列表进行排序时遇到了问题--按时间值是原生的。我在网上找不到答案。你有什么意见建议？

我的控制台登录原始对象的铬：

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防火墙数据库结构

​

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JSON.stringify(myObject)输出：

myObject={"-LAqmXKSdVVH6wirFa-g": 
{"desc":"fdf","price":"rrrr","receiveHelp":true,"subject":"Single Variable 
Calculus","time":1524558865757,"title":"Test1"},"-LAqmZlBFGoygfTsGQ0e": 
{"desc":"dsfdsfd3","price":"333","receiveHelp":true,"subject":"Single 
Variable Calculus","time":1524558875724,"title":"Test2"},"- 
LAqmcipUjlwLWTrRCw4": 
{"desc":"werwerwe55","price":"44","receiveHelp":true,"subject":"Single 
Variable Calculus","time":1524558891956,"title":"Test3"},"- 
LArMeYfHG6QMg_Frn9A": 
{"desc":"3","price":"3","receiveHelp":true,"subject":"Single Variable 
Calculus","time":1524568598762,"title":"Annons 1"},"-LArMjg5MkF5cMPZd_Fz": 
{"desc":"2222","price":"2","receiveHelp":true,"subject":"Single Variable 
 Calculus","time":1524568619782,"title":"Annons2"},"-LArNM-3Ij60XmSOBwvr": 
{"desc":"22","price":"","receiveHelp":true,"subject":"Single Variable 
 Calculus","time":1524568780803,"title":"Hej1"},"-LArNPugIfX1pPVZJ11e": 
{"desc":"f","price":"2","receiveHelp":true,"subject":"Single Variable 
 Calculus","time":1524568796844,"title":"Hej2f"}}

到目前为止，我已经尝试过：

firebase.database().ref('/users').once('value').then((snapshot) => {
const ads = snapshot.val();
let myObject = {};
Object.keys(ads).map((objectKey) => {
  const value = ads[objectKey];
  myObject = Object.assign(value.ads, myObject);
});

//Here i want to sort myObject by time and get the latest first

console.log(myObject)

Answer 1

您首先需要将广告或所有用户组合到一个数组中，然后进行排序。

​

let sortedAdds = Object.keys(usersData)
.reduce((prev, userId) => {
	let ads = usersData[userId].ads;
  ads = Object.keys(ads).map(key => {
     return { ...ads[key], id: key };
  });
  return prev.concat(ads);
}, [])
.sort((a, b) => (a.time - b.time));

​

Answer 2

([obj1, obj2]).sort((tm1, tm2) => {
  if (tm1.time > tm2.time) {
    return 1;
  }
  if (tm1.time < tm2.time) {
    return -1;
  }
  return 0;
})

Answer 3

您可以使用Firebase数据库的排序功能，而不是在前端进行排序，方法是：

var ref = database.ref('users/' + adId + '/ads').orderByChild('time');

如果您然后循环此查询的结果，广告将按时间排序。

ref.once('value', function(snapshot) {
    snapshot.forEach(function(childSnapshot) {
        var childData = childSnapshot.val();
        console.log(childData);
    });
});

编辑:如果你想拥有我理解为“最新的应该是第一次”的“最新的第一次”，那么你应该存储time*(-1)而不是time (time是unix时代以来的毫秒，如你的问题中所示)