Angular 6 with lowdb - not getting it to work - json

Question

I'm trying to create an Electron app with Angular 6 that uses lowdb as a local database.
It's all very new to me and it's trial and error, but I don't seem to be able to figure out how to overcome the following error:
I've installed lowdb in my application by using the commands
npm install --save lowdb (edit: forgot to mention I did this already)
and
npm install --save #types/lowdb
I've created a service to communicate with this "local database".
import { Injectable } from '#angular/core';
import lowdb from 'lowdb';
import { default as FileAsync } from 'lowdb/adapters/FileAsync';
import { CurrentUserModel } from '../models/current-user';
#Injectable({
providedIn: 'root'
})
export class LowdbService {
private db: lowdb.LowdbAsync;
constructor() {
this.initDatabase();
}
set( field: string, value: any ) {
this.db.set( field, value ).write();
}
private async initDatabase() {
const adapter = new FileAsync( 'db.json' );
this.db = await lowdb( adapter );
this.db.defaults( { user: CurrentUserModel } );
}
}
But when I include the service in the constructor of a component I get errors.
ERROR in ./src/app/services/lowdb.service.ts
Module not found: Error: Can't resolve 'lowdb' in '/Users/paul/Projects/application-name/src/app/services'
ERROR in ./src/app/services/lowdb.service.ts
Module not found: Error: Can't resolve 'lowdb/adapters/FileAsync' in '/Users/paul/Projects/application-name/src/app/services'
ℹ ｢wdm｣: Failed to compile.
ERROR in src/app/services/lowdb.service.ts(2,12): error TS1192: Module '"/Users/paul/Projects/application-name/node_modules/#types/lowdb/index"' has no default export.
src/app/services/lowdb.service.ts(3,14): error TS2305: Module '"/Users/paul/Projects/application-name/node_modules/#types/lowdb/adapters/FileAsync"' has no exported member 'default'.
As far as I can see I'm doing the same as mentioned in this Github comment and this Stackoverflow comment. I can't find any more documentation though.
Can somebody help me out?
Update
Using import * as lowdb from 'lowdb' seemed to solve my initial errors. But it resulted in a few other errors. See below.
ERROR in ./node_modules/graceful-fs/polyfills.js
Module not found: Error: Can't resolve 'constants' in '/Users/paul/Projects/project-name/node_modules/graceful-fs'
ERROR in ./node_modules/graceful-fs/graceful-fs.js
Module not found: Error: Can't resolve 'fs' in '/Users/paul/Projects/project-name/node_modules/graceful-fs'
ERROR in ./node_modules/graceful-fs/fs.js
Module not found: Error: Can't resolve 'fs' in '/Users/paul/Projects/project-name/node_modules/graceful-fs'
ERROR in ./node_modules/graceful-fs/legacy-streams.js
Module not found: Error: Can't resolve 'stream' in '/Users/paul/Projects/project-name/node_modules/graceful-fs'

Answer 1

First of all, if you installed just #types/lowdb, that is only typings for that library, you need to install the library itself via:
npm install --save lowdb
Then, looks like there is no default export so import lowdb from 'lowdb'; also won't work. Try is like this:
import { LowdbAsync } from 'lowdb';
import * as lowdb from 'lowdb';
import * as FileAsync from 'lowdb/adapters/FileAsync';
private db: LowdbAsync<any>; // TODO provide correct schema instead of any
private async initDatabase() {
const adapter = new FileAsync('db.json');
this.db = await lowdb(adapter);
this.db.defaults({ user: any });
}
Or you can try removing those typings (as they might be outdated) and do what their docs says:
https://github.com/typicode/lowdb/tree/master/examples#browser
import low from 'lowdb'
import LocalStorage from 'lowdb/adapters/LocalStorage'
(but when you take a look at #types/lowdb, there is no such default export so again, the typings might be outdated)
As for your other issue, take a look here:
https://github.com/typicode/lowdb/issues/206#issuecomment-324884867
typicode commented on 25 Aug 2017
#DickyKwok I think it's impossible. Can you answer this, #typicode?
I confirm, to save to disk using FileSync or FileAsync adapters you need to have access to Node fs API.
Looks like you should use LocalStorage adapter instead.
Another similar issue here: How can I use node "fs" in electron within angular 5
You could also try the solution proposed in one of answers there:
https://github.com/ThorstenHans/ngx-electron
constructor(private _electronService: ElectronService) {
this.fs = this._electronService.remote.require('fs');
}

Answer 2

Looks like your lowdb is missing in node_modules.
try
npm install lowdb