Visibility hidden in Angular 4

<!DOCTYPE html>
<html>

  <head>
  <base href="." />
    <title>ng-bootstrap demo</title>
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.6/css/bootstrap.min.css" />
    <script src="https://unpkg.com/core-js@^2.4.1/client/shim.js"></script>
    <script src="https://unpkg.com/zone.js@0.8.10/dist/zone.js"></script>
    <script src="https://unpkg.com/zone.js@0.8.10/dist/long-stack-trace-zone.js"></script>
    <script src="https://unpkg.com/reflect-metadata@^0.1.8/Reflect.js"></script>
    <script src="https://unpkg.com/systemjs@^0.19.40/dist/system.js"></script>
    <script src="config.js"></script>
    <script>
    System.import('app').catch(console.error.bind(console));
</script>
  </head>

  <body>
  <my-app>loading...</my-app>
  </body>

</html>

var ver = {
    ng: '4.0.3'
  };
  
  System.config({
  //use typescript for compilation
  transpiler: 'typescript',
  //typescript compiler options
  typescriptOptions: {
    emitDecoratorMetadata: true
  },
  paths: {
    'npm:': 'https://unpkg.com/'
  },
    map: {

    'app': './src',

    '@angular/core': 'npm:@angular/core@' + ver.ng + '/bundles/core.umd.js',
    '@angular/common': 'npm:@angular/common@' + ver.ng + '/bundles/common.umd.js',
    '@angular/compiler': 'npm:@angular/compiler@' + ver.ng + '/bundles/compiler.umd.js',
    '@angular/platform-browser': 'npm:@angular/platform-browser@' + ver.ng + '/bundles/platform-browser.umd.js',
    '@angular/platform-browser-dynamic': 'npm:@angular/platform-browser-dynamic@' + ver.ng + '/bundles/platform-browser-dynamic.umd.js',
    '@angular/http': 'npm:@angular/http@' + ver.ng + '/bundles/http.umd.js',
    '@angular/router': 'npm:@angular/router@' + ver.ng + '/bundles/router.umd.js',
    '@angular/forms': 'npm:@angular/forms@' + ver.ng + '/bundles/forms.umd.js',

    'rxjs': 'npm:rxjs@^5.0.1',
    'typescript': 'npm:typescript@2.1.5/lib/typescript.js',

    'angular-star-rating': 'npm:angular-star-rating'
  },
  packages: {
    app: {
      main: './main.ts',
      defaultExtension: 'ts'
    },
    rxjs: {
      defaultExtension: 'js'
    }
  }
});

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

platformBrowserDynamic().bootstrapModule(AppModule);


import { Component, NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { FormsModule, ReactiveFormsModule } from '@angular/forms';
import { JsonpModule } from '@angular/http';

@Component({
  selector: 'my-app',
  template: `
    <div class="container-fluid">
    <hr>
    <label for="chkVisible">Middle div visible:</label> <input id="chkVisible" type="checkbox" [(ngModel)]="isMiddleDivVisible" />
    <div id="div1"></div>
    <div id="div2" [style.visibility]="isMiddleDivVisible ? 'visible' : 'hidden'"></div>
    <div id="div3"></div>
  </div>
  `,
  styles: [
    `
    div { height: 50px; }
    #div1 { background-color: orange; }
    #div2 { background-color: green; }
    #div3 { background-color: red; }
    `]
})
export class App {
  isMiddleDivVisible: boolean = true;
}   

@NgModule({
  imports: [BrowserModule, FormsModule, ReactiveFormsModule, JsonpModule], 
  declarations: [App]
  bootstrap: [App]
}) 
export class AppModule {

}