How do I get data to display in Angular from API in Express?

Question

I am trying to use Nodejs/Express as my back end for producing data from a database. I currently have an api route setup so that a database query will result in its directory. So if I visit localhost:3000/api currently I will see the following:

 {"status":200,"data":[{"Issuer_Id":1,"Data_Id":2,"Data_Name":"Name 1"},{"Issuer_Id":2,"Data_Id":14,"Data_Name":"Name 2"},{"Issuer_Id":2,"Data_Id":1,"Data_Name":"Name 3"}],"message":null}

This leads me to believe I have everything setup correctly on the back end.

Now how do I get this data to display on my Angular front end?

I have been through hours of tutorials and this is what I have come up with:

nav.component.ts

 import { Component, OnInit } from '@angular/core'; import { DataService } from '../../data.service'; import { Series } from '../../data.service'; import {Observable} from 'rxjs/Rx'; @Component({ selector: 'app-fixed-nav', templateUrl: './fixed-nav.component.html', styleUrls: ['./fixed-nav.component.css'] }) export class FixedNavComponent implements OnInit{ serieses: Series[] ; constructor(private dataService: DataService) {} ngOnInit() { this.dataService.getSeries().subscribe((serieses: Series[]) => this.serieses = serieses); } }

data.service.ts

 import { Injectable } from '@angular/core'; import { HttpClient } from'@angular/common/http'; import { Http, Headers, RequestOptions, Response } from '@angular/http'; import { Observable } from 'rxjs/Observable'; import 'rxjs/add/operator/map'; import 'rxjs/add/operator/catch'; import 'rxjs/add/observable/throw'; import 'rxjs/add/operator/do'; import 'rxjs/add/operator/toPromise'; export class Series { Issuer_Id: number; Data_Id: number; Data_Name: string; } @Injectable() export class DataService { constructor(private _http: Http) {} getSeries(): Observable<Series[]> { return this._http.get("http://localhost:3000/api/") .map((res: Response) => res.json()); } }

app.module.ts

 import { Form1Module } from './modules/form1/form1.module'; import { FixedNavModule } from './modules/fixed-nav/fixed-nav.module'; import { HeaderModule } from './modules/header/header.module'; import { BrowserModule } from '@angular/platform-browser'; import { NgModule } from '@angular/core'; import { NgbModule } from '@ng-bootstrap/ng-bootstrap'; import { AppComponent } from './app.component'; import { HttpClientModule } from '@angular/common/http'; import { HttpModule } from '@angular/http'; import { DataService } from './data.service'; @NgModule({ declarations: [ AppComponent ], imports: [ BrowserModule, HttpModule, HttpClientModule, HeaderModule, FixedNavModule, Form1Module, NgbModule.forRoot() ], providers: [DataService], bootstrap: [AppComponent] }) export class AppModule { }

What do I need to enter in the nav.component.html to see the results?

Also note that when I refresh my angular page on lcoalhost:4200 I can see that the GET request is hitting the /apiu/ on the 3000 express server.

Answer 1

I am trying to help with best practices which might help get the intended result. I will amend this answer as we troubleshoot and hopefully arrive at the right answer.

So in your dataServices service I wanted to point out a couple things. Angular recommends we use the httpClient and not http and warn that http will soon be depreciated. I am fairly new to angular myself and have only ever used httpClient and have gotten great results so I recommend using that. I think this means that the promise that you are returned is changed too. Namely, you pust use a .pipe method inorder to use rxjs operators like map on the result. So this is what your dataService file would look like:

import { Injectable } from '@angular/core';
import { HttpClient } from'@angular/common/http';
import { Http, Headers, RequestOptions, Response } from '@angular/http';
import { Observable } from 'rxjs/Observable';

import { map } from 'rxjs/operators';
import 'rxjs/add/operator/catch';
import 'rxjs/add/observable/throw';
import 'rxjs/add/operator/do';
import 'rxjs/add/operator/toPromise';

export class Series {
  Issuer_Id: number;
  Data_Id: number;
  Data_Name: string;
}


@Injectable()
export class DataService {
  constructor(private _http: HttpClient) {}

  getSeries(): Observable<Series[]> {
    return this._http.get<Series[]>("http://localhost:3000/api/")
    .pipe(
      map((res) => {
        console.log(res);
        return <Series[]> res
      })
    )
  }
}

Note that I have imported map in a different rxjs/operators. In actuality you dont even need to pipe or map the return since you have already declared the type of return in the get method of _http. HttpClient will cast the return into a Series[] for you so this one liner: return this._http.get("http://localhost:3000/api/") would work. I've written the code how it is however to console.log the return that your getting.

In the comments, could you tell me what is logged?

Answer 2

I am unable to correct your code I am providing my own setup Works for Me

In server.js

module.exports.SimpleMessage = 'Hello world';

Now in App.js

var backend = require('./server.js');
console.log(backend.SimpleMessage); 
var data = backend.simpleMessage

In index html include App.js

<script src = '/App.js'></script>
alert(simpleMessage)

And you should get 'hello world'