LokiJS returns null database within module

I am creating a noSQL database for a NodeJS application. I want the database to exist as its own class. However, after moving my database initialization code inside the module it no longer works. LokiJS fails to load the database and I am unable to create collections. The result of loading a database is null, this.db is undefined and attempting to get a collection produces an Uncaught TypeError: Cannot read property 'getCollection' of undefined.

module.exports = Database;
function Database() {
    this.db;
    this.videos;
    this.playlists;

    this.init = function () {
        const loki = require("lokijs");
        const lfsa = require('../../node_modules/lokijs/src/loki-fs-structured-adapter.js');

        var adapter = new lfsa();
        this.db = new loki(`${localPath}db.json`, { adapter: adapter, autoload: true, autosave: true, autosaveInterval: 4000 });
        this.db.loadDatabase({}, function (result) {
            console.log(result); // This is null
            alert(this.db); // This is undefined
            alert(this.db.getCollection("SampleCollection")); // Uncaught TypeError: Cannot read property 'getCollection' of undefined
        });
    }
}

Your scope changes in the callback. The simplest way would be to use an arrow function instead:

this.db.loadDatabase({}, result => {
            console.log(result); // This is null
            alert(this.db); // This is undefined
            alert(this.db.getCollection("SampleCollection")); // Uncaught TypeError: Cannot read property 'getCollection' of undefined
        });