Read a JSON asynchronously and create an observable out of it.

app.ts

/**
 * Created by Davide Pugliese on 26/02/17.
 */
import {Observable, Subscribable} from "rxjs/Observable";
import "rxjs/add/observable/from";
import "rxjs/add/observable/fromPromise";
import "rxjs/add/observable/of";
import "rxjs/add/operator/map";
import "rxjs/add/observable/defer";


import * as path from 'path';
import {Observer, Subject} from "rxjs";
// const request = require('request');
const fs = require('fs');
const Promise = require('promise');

interface IUser {
    id: String;
    pw: String;
}

class User {
    public id;
    public pw;
}

class UserFactory {

    build()  {

        //We create a promise in order to decouple this precise "user feed" from the rest of the code.
        //In other words the code is ready for multiple "user feeds" as for example an API without having to refactor
        //later on.

        let readFile = Promise.denodeify(require('fs').readFile);

        return readFile(path.join(__dirname, '..', '.env.json'), 'utf8')
            .then(
                (x) => {
                    let a = JSON.parse(x);

                    let user = new User();

                    user.id = a.id;
                    user.pw = a.pw;

                    // console.log(JSON.stringify(user));
                    return user;
                }
            );
    }
}

let user  = new UserFactory();

let userObservable = Observable.from(user.build());

userObservable.subscribe(x => console.log(JSON.stringify(x)));