JS:firebase.init错误:TypeError:无法读取未定义的属性“数据库"

按照nativescript-plugin-firebase自述文件中提到的步骤操作后，出现此错误.

Am getting this error after following the steps mentioned in the nativescript-plugin-firebase readme file.

JS:firebase.init错误:TypeError:无法读取以下属性的数据库" 未定义

JS: firebase.init error: TypeError: Cannot read property 'database' of undefined

https://github.com/EddyVerbruggen/nativescript-plugin-firebase

但是我真的不明白，我也不知道该怎么解决.

but i dont really understand nor do i know how to solve that.

正在使用的插件版本为:6.4.0 使用tns 4.1.2

the version of the plugin am using is : 6.4.0 with tns 4.1.2

var firebase = require("nativescript-plugin-firebase");
firebase.init({ persist: true
    // Optionally pass in properties for database, authentication and cloud messaging,
    // see their respective docs.
}).then(
    function (instance) {
    console.log("firebase.init done");
    },
    function (error) {
    console.log("firebase.init error: " + error);
    }
);