如果要在受信任的服务器上通过电子邮件查找用户，则可以使用Firebase Admin SDK.从有关检索用户数据的文档:

If you want to look up a user by their email on a trusted server, you can use the Firebase Admin SDK. From the documentation on retrieving user data:

admin.auth().getUserByEmail(email)
  .then(function(userRecord) {
    // See the tables above for the contents of userRecord
    console.log("Successfully fetched user data:", userRecord.toJSON());
  })
  .catch(function(error) {
    console.log("Error fetching user data:", error);
  });

用于Firebase身份验证的客户端SDK仅提供对当前已身份验证用户的配置文件的访问.他们没有提供通过电子邮件地址查找用户的方法.要允许客户端查找，通常的方法是将UID-by-email-address存储在数据库中:

The client SDKs for Firebase Authentication only provide access to the profile of the currently authenticated user. They don't provide a way to look up a user by their email address. To allow client-side lookup, the common way to do so is to store the UID-by-email-address in the database:

"emailToUid": {
    "SumOne@domain,com": "uidOfSumOne",
    "puf@firebaseui,com": "uidOfPuf"
}

通过此简单列表，您可以从以下位置通过编码的电子邮件地址查找UID:

With this simple list, you can look up the UID by the encoded email address from:

ref.child("emailToUid").child("SumOne@domain,com").addSingleValueEventListener(...

另请参阅:

• Firebase身份验证服务-无需登录即可从电子邮件中查找uid
• 在Firebase用户表上添加其他详细信息
• 如何从Firebase数据库获取经过身份验证的用户?

• Firebase Authentication Service - lookup uid from email without login
• Add Extra Details on Firebase User Table
• How to get authenticated users from firebase database?