Firebase ref.on("value"即使没有值更改也被调用-node.js [英] Firebase ref.on("value" is getting called even without a change in value - node.js

问题描述

我正在尝试观察我的Firebase数据库中的更改.

I am trying to observe a change in my firebase DB.

这是我的结构

数据库-身份验证:正确

DB - Authenticate : true

我正在我的node.js应用程序中收听身份验证"中的更改

I am listening to changes in Authenticate like this in my node.js app

var authRef = firebase.database().ref('Authentication');
      authRef.on('value', function(snapshot) {
              console.log(snapshot.val());
              res.send(snapshot.val());
      });

但是，一旦我调用 authRef.on ，它就会获取先前的值，而不是等待更改.

But as soon as I call authRef.on , it is fetching the previous value instead of waiting for a change.

请咨询.

推荐答案

这是Firebase侦听器的本质.
创建值侦听器时，它将至少获取一次数据.
为了防止这种情况，我将执行以下操作:

It is the nature of firebase listeners.
When you create a value listener it will fetch the data at least once.
I would do the following to prevent this:

var i = 0
var authRef = firebase.database().ref('Authentication');
  authRef.on('value', function(snapshot) {

          if( i != 0){
            console.log(snapshot.val());
            res.send(snapshot.val());
          }
          i++
  });

如果您这样做，它将不会考虑第一个电话

It will not consider the first call if you do so

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