Angular + Nodejs error CORS

employees-create.component.ts

import { Component, OnInit } from '@angular/core';
import { Empleado } from '../modelo-de-datos/empleados';
import { NgForm } from '@angular/forms';
import { EmpleadoServiceService } from '../servicios/empleado-service.service';


@Component({
  selector: 'app-empleados-crear',
  templateUrl: './empleados-crear.component.html',
  styleUrls: ['./empleados-crear.component.css'],
  providers:[EmpleadoServiceService]
})
export class EmpleadosCrearComponent implements OnInit {

  public a:number;
  public empleado_nuevo:Empleado;
  public fecha_nacimiento:Date;

  constructor(
    private empleadoService:EmpleadoServiceService

  ) {

  }

  ngOnInit() {
    this.fecha_nacimiento = new Date();


    this.empleado_nuevo = new Empleado('','','','',0,this.fecha_nacimiento);
   }

   limpiarFormulario(form?:NgForm){
    this.empleado_nuevo = new Empleado('','','','',0,this.fecha_nacimiento);
   }

   insertarEmpleado(){
    console.log(this.empleado_nuevo);
    //console.log(form.value)
    this.empleadoService.addEmpleado(this.empleado_nuevo).subscribe(
      res=>{
        console.log(res);
        },
        error=>{
          console.log(error);
        }
    );

   }

}

employee-service.service.ts

import { Injectable } from '@angular/core';
import { Empleado } from '../modelo-de-datos/empleados';

import { Observable } from 'rxjs';
import { HttpClient, HttpHeaders } from '@angular/common/http';

@Injectable({
  providedIn: 'root'
})

export class EmpleadoServiceService {

  private empleado: Empleado;
  private empleados: Empleado[];
  //readonly url_api = 'localhost:3000/getEmpleados';

  constructor(
    private http: HttpClient
  ) { }


  getEmpleados() {
    return this.http.get('localhost:3000/getEmpleados').subscribe(
      res=>{
        console.log(res);
      },
      error=>{
        console.log(error);
      }
    );
  }

  addEmpleado(empleado_nuevo: Empleado){
      return this.http.post('localhost:3000/addEmpleado',empleado_nuevo);

  }

}

Chrome Console

Empleado {dni: "66666666Z", nombre: "Luis", apellidos: "Rodriguez Guzman", departamento: "Prestamatica", sueldo: 12300, …}
apellidos: "Rodriguez Guzman"
departamento: "Prestamatica"
dni: "66666666Z"
fecha_nacimiento: "2018-11-08"
nombre: "Luis"
sueldo: 12300
__proto__: Object
zone.js:2969 Access to XMLHttpRequest at 'localhost:3000/addEmpleado' from origin 'http://localhost:4200' has been blocked by CORS policy: Cross origin requests are only supported for protocol schemes: http, data, chrome, chrome-extension, https.
empleados-crear.component.ts:46 
HttpErrorResponse {headers: HttpHeaders, status: 0, statusText: "Unknown Error", url: null, ok: false, …}
error: ProgressEvent {isTrusted: true, lengthComputable: false, loaded: 0, total: 0, type: "error", …}
headers: HttpHeaders {normalizedNames: Map(0), lazyUpdate: null, headers: Map(0)}
message: "Http failure response for (unknown url): 0 Unknown Error"
name: "HttpErrorResponse"
ok: false
status: 0
statusText: "Unknown Error"
url: null
__proto__: HttpResponseBase

Firefox console

error: error { target: XMLHttpRequest, isTrusted: true, lengthComputable: false, … }
​
headers: Object { normalizedNames: Map(0), lazyUpdate: null, headers: Map(0) }
​
message: "Http failure response for (unknown url): 0 Unknown Error"
​
name: "HttpErrorResponse"
​
ok: false
​
status: 0
​
statusText: "Unknown Error"
​
url: null
​
<prototype>: Object { constructor: HttpErrorResponse()
 }

index.js on my server in nodejs

const express = require('express');
const app = express();
const cors = require('cors');
const morgan = require('morgan');
const {mongoose} = require('./database');

//settings
app.set('port',3000);


//middleware
app.use(morgan('dev'));
app.use(express.json());

    app.use(cors({
        origin:'http://localhost:4200'
    }));



    //CORS -2 
    /*
   const corsOptions = {
    origin: [process.env.URL, 'http://localhost:4200']
  }
  */
  app.use(cors(corsOptions))
  app.options('*', cors(corsOptions))

  //FIN CORS 2

//routes
app.use(require('./routes/empleado.routes'));

//starting server
app.listen(3000,()=>{
    console.log('Servidor en el puerto '+app.get('port'));
});