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The currently logged in user is returned from Simple Login's callback. This callback runs when your user authenticates, or if your user is already authenticated, it runs at the time of page load.

当前登录的用户从Simple Login的回调中返回。此回调在用户进行身份验证时运行，或者如果您的用户已经过身份验证，则会在页面加载时运行。

Take this code form the simple login docs:

从简单的登录文档中获取此代码：

var myRef = new Firebase("https://<your-firebase>.firebaseio.com");
var authClient = new FirebaseSimpleLogin(myRef, function(error, user) {
  if (error) {
    // an error occurred while attempting login
    console.log(error);
  } else if (user) {
    // user authenticated with Firebase
    console.log("User ID: " + user.uid + ", Provider: " + user.provider);
  } else {
    // user is logged out
  }
});

The user object is exposed in the callback. It's only in scope during the execution of that callback, so if you want to use it outside, store it in a variable for reuse later like this:

用户对象在回调中公开。它只在执行该回调期间的范围内，因此如果您想在外部使用它，请将其存储在变量中以便稍后重复使用，如下所示：

var currentUser = {};
var myRef = new Firebase("https://<your-firebase>.firebaseio.com");
var authClient = new FirebaseSimpleLogin(myRef, function(error, user) {
  if (error) {
    // an error occurred while attempting login
    console.log(error);
  } else if (user) {
    // user authenticated with Firebase
    currentUser = user;
  } else {
    // user is logged out
  }
});
...

// Later on in your code (that runs some time after that login callback fires)
console.log("User ID: " + currentUser.uid + ", Provider: " + currentUser.provider);