Vue.js 使用 Firebase Auth for Google 将匿名用户转换为注册用户

我正在使用Firebase Auth和VueJS，我需要将anonymous auth user转换为registered one with Google.

我使用的代码来自一个示例:

  fromAnonymousToGoogle: function () {
  // Authenticate with the first user then save the currentUser to a local variable
    var previousUser = Firebase.auth().currentUser

  // Authenticate with a second method and get a credential
    var credential = Firebase.auth.GoogleAuthProvider()

    previousUser.link(credential)
    .catch(function (error) {
     // Linking will often fail if the account has already been linked. Handle these cases manually.
      alert(error)
    })

    // OAuth providers authenticate in an asynchronous manner, so you’ll want to perform the link account link in the callback.
    // previousUser = Firebase.auth().currentUser;
    Firebase.auth().signInWithPopup(new Firebase.auth.GoogleAuthProvider())
     .then(function (result) {
       return previousUser.link(result.credential)
     })
     .catch(function (err) {
       // Handle error
       alert(err)
     })
  },

我试图将该帐户链接到谷歌时出现此错误:

[Vue warn]:"单击"的事件处理程序出错:"类型错误:this.ta不是函数"

我的代码中没有名为this.ta的函数.如何修复此错误？