how to get the value of an arrow function in node.js

I want to get the value of the variable "final" to be able to send to the frontend through sockets

My code

const admin = database.collection("admin").onSnapshot(documento =>{
     const final = documento.docs.map((doc) =>({id: doc.id, ...doc.data()}))
     return final
})

const alerts = admin()

console.log(alerts);

//sockets
io.on('connection', function (socket) {
    console.log('Alguien se ha conectado con Sockets');

    socket.emit('alerts', alerts);
    socket.on('new-alert', function (data) {
        alerts.push(data);
        io.sockets.emit('alerts', alerts);
    });

}); 
//sockets

>Solution :

I would put the necessary logic to be executed when onSnapshot is called.

const admin = database.collection("admin").onSnapshot(documento =>{
     const final = documento.docs.map((doc) =>({id: doc.id, ...doc.data()}))
     // Code that uses final here
})