https://coryrylan.com/blog/listening-to-angular-key-events-with-host-listeners

<!DOCTYPE html>
<html>

  <head>
    <title>Angular Host Listeners and Key Events</title>
    <script src="https://unpkg.com/core-js/client/shim.min.js"></script>
    <script src="https://unpkg.com/zone.js@0.7.4?main=browser"></script>
    <script src="https://unpkg.com/systemjs@0.19.39/dist/system.src.js"></script>
    <script src="systemjs.config.js"></script>
    <script>
      System.import('app').catch(function(err){ console.error(err); });
    </script>
  </head>

  <body>
    <demo-app>Loading App...</demo-app>
  </body>
</html>

import { Component, HostListener } from '@angular/core';
import { Observable } from 'rxjs/Observable';
import { Subscription } from 'rxjs/Subscription';
import { of } from 'rxjs/observable/of';
import { delay, share } from 'rxjs/operators';

@Component({
  selector: 'demo-app',
  templateUrl: 'app/app.component.html'
})
export class AppComponent {
  user1: Observable<{}>;
  user2: {};
  user3: {};
  subscription: Subscription;
  
  constructor() { }
  
  ngOnInit() {
    // Using ngIf ngElse
    this.user = this.getAsyncData();
    
    // Using just async pipe
    this.user2 = this.getAsyncData().pipe(share());
    
    // Manual subscription handling
    this.subscription = this.getAsyncData().subscribe(u => this.user3 = u);
  }
  
  ngOnDestroy() {
    this.subscription.unsubscribe();
  }
  
  getAsyncData() {
     // Fake Slow Async Data
    return of({
      firstName: 'Luke',
      lastName: 'Skywalker',
      age: 65,
      height: 172,
      mass: 77,
      homeworld: 'Tatooine'
    }).pipe(
      delay(2000)
    );
  }
}

<h1>With ngIf and ngElse</h1>
<div *ngIf="user | async; let user; else loading;">
  <h2>{{user.firstName}} {{user.lastName}}</h2>
  <dl>
    <dt>Age:</dt>
    <dd>{{user.age}}</dd>

    <dt>Height:</dt>
    <dd>{{user.height}}</dd>

    <dt>Mass:</dt>
    <dd>{{user.mass}}</dd>

    <dt>Homeworld:</dt>
    <dd>{{user.homeworld}}</dd>
  </dl>
</div>
<ng-template #loading>Loading User Data...</ng-template>

<br>

<h2>Async Pipe with share() operator</h2>
<div>
  <h2>{{(user2 | async)?.firstName}} {{(user2 | async)?.lastName}}</h2>
  <dl>
    <dt>Age:</dt>
    <dd>{{(user2 | async)?.age}}</dd>

    <dt>Height:</dt>
    <dd>{{(user2 | async)?.height}}</dd>

    <dt>Mass:</dt>
    <dd>{{(user2 | async)?.mass}}</dd>

    <dt>Homeworld:</dt>
    <dd>{{(user2 | async)?.homeworld}}</dd>
  </dl>
</div>

<h2>Manual subscription Handling in TypEscript</h2>
<div>
  <h2>{{user3?.firstName}} {{user3?.lastName}}</h2>
  <dl>
    <dt>Age:</dt>
    <dd>{{user3?.age}}</dd>

    <dt>Height:</dt>
    <dd>{{user3?.height}}</dd>

    <dt>Mass:</dt>
    <dd>{{user3?.mass}}</dd>

    <dt>Homeworld:</dt>
    <dd>{{user3?.homeworld}}</dd>
  </dl>
</div>

/**
 * WEB ANGULAR VERSION
 * (based on systemjs.config.js in angular.io)
 * System configuration for Angular samples
 * Adjust as necessary for your application needs.
 */
(function (global) {
  System.config({
    // DEMO ONLY! REAL CODE SHOULD NOT TRANSPILE IN THE BROWSER
    transpiler: 'ts',
    typescriptOptions: {
      // Copy of compiler options in standard tsconfig.json
      "target": "es5",
      "module": "commonjs",
      "moduleResolution": "node",
      "sourceMap": true,
      "emitDecoratorMetadata": true,
      "experimentalDecorators": true,
      "lib": ["es2015", "dom"],
      "noImplicitAny": true,
      "suppressImplicitAnyIndexErrors": true
    },
    meta: {
      'typescript': {
        "exports": "ts"
      }
    },
    paths: {
      // paths serve as alias
      'npm:': 'https://unpkg.com/'
    },
    // map tells the System loader where to look for things
    map: {
      // our app is within the app folder
      'app': 'app',

      // angular bundles
      '@angular/animations': 'npm:@angular/animations/bundles/animations.umd.js',
      '@angular/animations/browser': 'npm:@angular/animations/bundles/animations-browser.umd.js',
      '@angular/core': 'npm:@angular/core/bundles/core.umd.js',
      '@angular/common': 'npm:@angular/common/bundles/common.umd.js',
      '@angular/common/http': 'npm:@angular/common/bundles/common-http.umd.js',
      '@angular/compiler': 'npm:@angular/compiler/bundles/compiler.umd.js',
      '@angular/platform-browser': 'npm:@angular/platform-browser/bundles/platform-browser.umd.js',
      '@angular/platform-browser/animations': 'npm:@angular/platform-browser/bundles/platform-browser-animations.umd.js',
      '@angular/platform-browser-dynamic': 'npm:@angular/platform-browser-dynamic/bundles/platform-browser-dynamic.umd.js',
      '@angular/http': 'npm:@angular/http/bundles/http.umd.js',
      '@angular/router': 'npm:@angular/router/bundles/router.umd.js',
      '@angular/router/upgrade': 'npm:@angular/router/bundles/router-upgrade.umd.js',
      '@angular/forms': 'npm:@angular/forms/bundles/forms.umd.js',
      '@angular/upgrade': 'npm:@angular/upgrade/bundles/upgrade.umd.js',
      '@angular/upgrade/static': 'npm:@angular/upgrade/bundles/upgrade-static.umd.js',

      // other libraries
      'rxjs':                      'npm:rxjs@5.5.2',
      'rxjs/operators':            'npm:rxjs@5.5.2/operators/index.js',
      'tslib':                     'npm:tslib/tslib.js',
      'angular-in-memory-web-api': 'npm:angular-in-memory-web-api@0.4/bundles/in-memory-web-api.umd.js',
      'ts':                        'npm:plugin-typescript@5.2.7/lib/plugin.js',
      'typescript':                'npm:typescript@2.4.2/lib/typescript.js',

    },
    // packages tells the System loader how to load when no filename and/or no extension
    packages: {
      app: {
        main: './main.ts',
        defaultExtension: 'ts',
        meta: {
          './*.ts': {
            loader: 'systemjs-angular-loader.js'
          }
        }
      },
      rxjs: {
        defaultExtension: 'js'
      }
    }
  });

})(this);

/*
Copyright 2016 Google Inc. All Rights Reserved.
Use of this source code is governed by an MIT-style license that
can be found in the LICENSE file at http://angular.io/license
*/

import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';

import { AppModule } from './app.module';

const platform = platformBrowserDynamic();
platform.bootstrapModule(AppModule);

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { HttpModule } from '@angular/http';
import { RouterModule } from '@angular/router';

import { AppComponent } from './app.component';

@NgModule({
  imports: [
    BrowserModule,
    HttpModule
  ],
  declarations: [
    AppComponent
  ],
  providers: [ ],
  bootstrap: [ AppComponent ]
})
export class AppModule {
}

{
  "compilerOptions": {
    "target": "es5",
    "module": "commonjs",
    "moduleResolution": "node",
    "sourceMap": true,
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true,
    "removeComments": false,
    "noImplicitAny": true,
    "suppressImplicitAnyIndexErrors": true
  }
}

var templateUrlRegex = /templateUrl\s*:(\s*['"`](.*?)['"`]\s*)/gm;
var stylesRegex = /styleUrls *:(\s*\[[^\]]*?\])/g;
var stringRegex = /(['`"])((?:[^\\]\\\1|.)*?)\1/g;

module.exports.translate = function(load){
  if (load.source.indexOf('moduleId') != -1) return load;

  var url = document.createElement('a');
  url.href = load.address;

  var basePathParts = url.pathname.split('/');

  basePathParts.pop();
  var basePath = basePathParts.join('/');

  var baseHref = document.createElement('a');
  baseHref.href = this.baseURL;
  baseHref = baseHref.pathname;

  if (!baseHref.startsWith('/base/')) { // it is not karma
    basePath = basePath.replace(baseHref, '');
  }

  load.source = load.source
    .replace(templateUrlRegex, function(match, quote, url){
      var resolvedUrl = url;

      if (url.startsWith('.')) {
        resolvedUrl = basePath + url.substr(1);
      }

      return 'templateUrl: "' + resolvedUrl + '"';
    })
    .replace(stylesRegex, function(match, relativeUrls) {
      var urls = [];

      while ((match = stringRegex.exec(relativeUrls)) !== null) {
        if (match[2].startsWith('.')) {
          urls.push('"' + basePath + match[2].substr(1) + '"');
        } else {
          urls.push('"' + match[2] + '"');
        }
      }

      return "styleUrls: [" + urls.join(', ') + "]";
    });

  return load;
};