如何在Firebase上随机获取相同的数据？

Question

我有用户表和这段代码.

getOnline代码和连接按钮

var onlineStatus = firebase.database().ref("users/" + firebase.auth().currentUser.uid + "/online");
onlineStatus.set(1);  

和

var dbUser = firebase.database();
var refUser = dbUser.ref("users");


refUser.orderByChild("online").equalTo(1).on("value", function(Data){
    console.log(Data.val(), Data.key);
});

我已经可以看到在线= 1个用户,但我想随机获得1个在线= 1的用户.

我怎样才能做到这一点？

更新

我想建立随机聊天.人们会根据标准进行匹配.喜欢Tinder App.想想看,有一个页面和按钮.当用户按下按钮时,它将匹配任何在线用户.和聊天.

firebase用户;

users
     VIkvYAtLHxNqAwd722oKenriM7PJz2
        email: "mail@hotmail.com"
        online: 1 
        profile_picture:"https://scontent.xx.fbcdn.net" 
        username: "John Snow"

     DIkvYAtLHxNqAwd722oKenriM7PJz2
        email: "mail2@hotmail.com"
        online: 1 
        profile_picture:"https://scontent.xx.fbcdn.net" 
        username: "Jane Snow"

Answer 1

您可以使用Math.random()函数获取一个随机数(让我们称之为n),然后让第n个用户在线:

refUser.orderByChild("online").equalTo(1).on("value", function(Data){
    console.log(Data.val(), Data.key);
    var totalOnline = Data.numChildren(); //get number of online users
    var randomNr = Math.random() * totalOnline;
    var userIndex = parseInt(randomNr, 10); //parse the random number from double to integer
    var currentIndex = 0;
    Data.forEach(function(snap){
        if(currentIndex==userIndex){
            var randomUser = snap.val();
            //Do something with your random user
            break;
        }
        currentIndex++;
    });
});

另请注意,如果您拥有包含数千名用户的庞大应用,则可能需要将查询限制为50位用户以提高应用的效果:

refUser.orderByChild("online").equalTo(1).limitToFirst(50)

更新:要排除您自己的用户,您可以检查随机用户是否是您.如果是,请转到下一个:

        if(currentIndex>=userIndex && snap.key != firebase.auth().currentUser.uid){
            var randomUser = snap.val();
            //Do something with your random user
            break;
        }

更新2:我发现你不能使用breakon forEach循环.所以你可以使用这里提供的解决方案来解决这个问题(使用BreakException):

refUser.orderByChild("online").equalTo(1).on("value", function(Data){
    console.log(Data.val(), Data.key);
    var totalOnline = Data.numChildren(); //get number of online users
    var randomNr = Math.random() * totalOnline;
    var userIndex = parseInt(randomNr, 10); //parse the random number from double to integer
    var currentIndex = 0;
    var BreakException = {};
    try
    {
        Data.forEach(function(snap){
            if(currentIndex==userIndex){
                var randomUser = snap.val();
                //Do something with your random user
                throw BreakException;
            }
            currentIndex++;
        });
    }
    catch(e){
        if(e!== BreakException) throw e;
    }
});