Node.JS MongoDB client connection

mongoClient.js

"use strict";

/**
Usage: 

const client = require("/path/to/this/file")

async function someFunction(){
	//...
	const db = await client.db();
	db.collection("user").findOne({}); 
	db.close();
	// ...
}
**/


const fs = require("fs");
const mongoDB = require("mongodb");
const config = require("/path/to/config") /*change this to a config file which has a db name as "db" property */

const url = "mongodb://127.0.0.1:27017"; /*change this to mongo server uri*/

const WRITE_ERR_LOGS_TO_FILE = true; /*no log file if false */

class Client {
	constructor() {

		//copy all props of mongodb 
		Object.assign(this, mongoDB);

		this._client = null;
		this._connect = this._connect.bind(this);

		this.dbName = config.db;
		this.getDB = this.getDB.bind(this);
	}

	async _connect() {

		if (!this._client) {
			try {

				this._client = await mongoDB.MongoClient.connect(url, { useNewUrlParser: true, useUnifiedTopology: true });
				return this._client; //as of mongodb 4.0.13 MongoClient.connect return client object

			} catch (err) {

				if (WRITE_ERR_LOGS_TO_FILE) {
					fs.appendFile("./mongoError.log", JSON.stringify(err, null, 4), (fileWriteError) => {
						if (fileWriteError) console.log(fileWriteError) // :| what else to do ? lol :p
					});
				}

				console.log(err);
				throw err;
			}
		}

		return this._client;
	}


	async getClient() {

		//return client if already connected
		if (this._client) return this._client;

		//or create new client and return
		return await this._connect();
	}

	async getDB(dbName = this.dbName) {

		if (!this._client) await this._connect();

		let db = this._client.db(dbName);
		return db;
	}

	async getCollection(collectionName, dbName = this.dbName) {
		if (!this._client) await this._connect();

		let collection = this._client.db(dbName).collection(collectionName);
		return collection;
	}

	async closeClient() {
		if (this._client) {
			await this._client.close();
			this._client = null;
		}

	}
}

module.exports = new Client();