javascript中的Firebase全局访问子级

问题描述

我想在我的整个javascript文件中访问并使用firebase db子级.

I want to access and use a firebase db child across my whole javascript file.

这是我的数据库的样子:

This is how my db looks like:

  var bidAUDUSD;
  var audusd = firebase.database().ref('Symbols/AUDUSD/bid').once('value')
.then(function(snapshot){
      bidAUDUSD = snapshot.val();
      console.log(bidAUDUSD); // this prints the bid;
    });
 console.log(bidAUDUSD); //this prints undefined;

任何想法如何在全球范围内使用?预先感谢！

Any ideas how can I use it globally? Thanks in advance!

推荐答案

"then"许诺将花费一些时间来打印快照，但是在您的情况下，您在调用"then"之前就打印了全局变量.因此，您可以做的是在"then" promise内调用一个函数，然后尝试打印全局变量，如我在下面的代码所示.

"then" promise will take sometime to print the snapshot, but in your case you printed the global variable before the "then" is called. So what you can do is call a function inside the "then" promise and then try print the global variable like I coded below.

var bidAUDUSD;
var audusd = firebase.database().ref('Symbols/AUDUSD/bid').once('value')
.then(function(snapshot){
  bidAUDUSD = snapshot.val();//"then" promise will take some time to execute, so only the bidAUDUSD is undefined in the outside console log. 
// what you can do is call a function inside the "then" promise and then print the console log like below. 
  _callConsoleLog(bidAUDUSD);
  console.log(bidAUDUSD); // this prints the bid;
});

var _callConsoleLog=function(bidId){
   // try to print it here. 
   console.log(bidId)// either you can print the parameter that is passed or
   console.log(bidAUDUSD) // your global variable.
}

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