nuxt-promote-yourself/server/dbMocks/seedDb.js

const mongoose = require('mongoose');
const User = require('../models/user');
const data = require('./data.js');
const keys = require('../keys');

class DB {
  constructor() {
    this.collections = Object.keys(data).map(collection => collection);
  }

  async cleanDb() {
     for (let collection of this.collections) {
      var model = data[collection].model;
      if (model) {
        await model.deleteMany({}, () => {});
        console.log(`Data for model ${model.collection.collectionName} Deleted!`)
      }
    }
  }

  async pushDataToDb() {
    var collectionToResolve = [];
    for (let collection of this.collections) {
      collectionToResolve.push(Promise.all(
        data[collection].items.map(item =>
         (new data[collection].model(item)).save()
        )
      ).then(data => console.log(collection, 'collection saved!')))
    }

    return Promise.all(collectionToResolve);
  }

  async seedDb() {
    await this.cleanDb();
    await this.pushDataToDb();
    console.log('Data Populated!')
  }
}

mongoose.connect(keys.DB_URI, { useNewUrlParser: true })
  .then(async () => {
    const db = new DB();
    await db.seedDb();
    console.log('You can close connection now!')
  })
  .catch(err => console.log(err));