<ul id="links">
    <li>
        <a href="/">Home</a>
    </li>
    <li>
        <a href="/census">Census</a>
    </li>
    <li>
        <button (click)="login()">Login</button>
    </li>
</ul>

import { Component, OnInit } from '@angular/core';
import { Router } from '@angular/router';

import { AuthenticationService } from '../_services/Authentication.Service';

@Component({
  selector: 'app-header',
  templateUrl: './header.component.html',
  styleUrls: ['./header.component.css']
})
export class HeaderComponent implements OnInit {

  constructor(private _auth: AuthenticationService, private router: Router) { }

  ngOnInit() {
  }

  login() {
        this.loading = true;
        this._auth.login(this.model.username, this.model.password)
            .subscribe(result => {

            });
    }

}

import { Injectable } from '@angular/core';
import { Http, Headers, Response, RequestOptions } from '@angular/http';
import { Observable } from 'rxjs';
import 'rxjs/add/operator/map'

@Injectable()
export class AuthenticationService {
    public token: string;

    constructor(private http: Http) {
        // set token if saved in local storage
        var currentUser = JSON.parse(localStorage.getItem('currentUser'));
        this.token = currentUser && currentUser.token;
    }

    login(usn: string, psw: string): Observable<boolean> {
        let headers = new Headers({ 'Content-Type': 'application/json' });
        let options = new RequestOptions({ headers: headers });
        return this.http.post('http://localhost:5000/auth', JSON.stringify({ username: "email-removed", password: "password-removed" }), options)
                    .map((response: Response) => { return true; });
    }
}