Directive Scroll - Angular 4

<!DOCTYPE html>
<html>

  <head>
    <base href="." />
    <script type="text/javascript" charset="utf-8">
      window.AngularVersionForThisPlunker = 'latest'
    </script>
    <title>angular playground</title>
    <link rel="stylesheet" href="style.css" />
    <script src="https://unpkg.com/core-js@2.4.1/client/shim.min.js"></script>
    <script src="https://unpkg.com/zone.js/dist/zone.js"></script>
    <script src="https://unpkg.com/zone.js/dist/long-stack-trace-zone.js"></script>
    <script src="https://unpkg.com/reflect-metadata@0.1.3/Reflect.js"></script>
    <script src="https://unpkg.com/systemjs@0.19.31/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>

/* Styles go here */

.box{
  height: 200px; 
  border: 1px solid red; 
  overflow:scroll;
}

### Angular Starter Plunker - Typescript

var angularVersion;
if(window.AngularVersionForThisPlunker === 'latest'){
  angularVersion = ''; //picks up latest
}
else {
  angularVersion = '@' + window.AngularVersionForThisPlunker;
}

System.config({
  //use typescript for compilation
  transpiler: 'typescript',
  //typescript compiler options
  typescriptOptions: {
    emitDecoratorMetadata: true
  },
  paths: {
    'npm:': 'https://unpkg.com/'
  },
  //map tells the System loader where to look for things
  map: {
    
    'app': './src',
    '@angular/core': 'npm:@angular/core'+ angularVersion + '/bundles/core.umd.js',
    '@angular/common': 'npm:@angular/common' + angularVersion + '/bundles/common.umd.js',
    '@angular/compiler': 'npm:@angular/compiler' + angularVersion  + '/bundles/compiler.umd.js',
    '@angular/platform-browser': 'npm:@angular/platform-browser' + angularVersion + '/bundles/platform-browser.umd.js',
    '@angular/platform-browser-dynamic': 'npm:@angular/platform-browser-dynamic' + angularVersion + '/bundles/platform-browser-dynamic.umd.js',
    '@angular/http': 'npm:@angular/http' + angularVersion + '/bundles/http.umd.js',
    '@angular/router': 'npm:@angular/router' + angularVersion +'/bundles/router.umd.js',
    '@angular/forms': 'npm:@angular/forms' + angularVersion + '/bundles/forms.umd.js',
    '@angular/animations': 'npm:@angular/animations' + angularVersion + '/bundles/animations.umd.js',
    '@angular/platform-browser/animations': 'npm:@angular/platform-browser' + angularVersion + '/bundles/platform-browser-animations.umd.js',
    '@angular/animations/browser': 'npm:@angular/animations' + angularVersion + '/bundles/animations-browser.umd.js',
    
    '@angular/core/testing': 'npm:@angular/core' + angularVersion + '/bundles/core-testing.umd.js',
    '@angular/common/testing': 'npm:@angular/common' + angularVersion + '/bundles/common-testing.umd.js',
    '@angular/compiler/testing': 'npm:@angular/compiler' + angularVersion + '/bundles/compiler-testing.umd.js',
    '@angular/platform-browser/testing': 'npm:@angular/platform-browser' + angularVersion + '/bundles/platform-browser-testing.umd.js',
    '@angular/platform-browser-dynamic/testing': 'npm:@angular/platform-browser-dynamic' + angularVersion + '/bundles/platform-browser-dynamic-testing.umd.js',
    '@angular/http/testing': 'npm:@angular/http' + angularVersion + '/bundles/http-testing.umd.js',
    '@angular/router/testing': 'npm:@angular/router' + angularVersion + '/bundles/router-testing.umd.js',
    'tslib': 'npm:tslib@1.6.1',
    'rxjs': 'npm:rxjs',
    'typescript': 'npm:typescript@2.2.1/lib/typescript.js'
  },
  //packages defines our app package
  packages: {
    app: {
      main: './main.ts',
      defaultExtension: 'ts'
    },
    rxjs: {
      defaultExtension: 'js'
    }
  }
});

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

platformBrowserDynamic().bootstrapModule(AppModule)

//our root app component
import {Component, VERSION} from '@angular/core'

@Component({
  selector: 'my-app',
  templateUrl: 'src/app.component.html'
})
export class AppComponent {
}

import {NgModule} from '@angular/core';
import {BrowserModule} from '@angular/platform-browser';


import {AppComponent} from './app.component';
import {BoxComponent} from './box.component';
import {ScrollDirective} from './directives/scroll.directive.ts';

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

<box></box>
<box></box>

import { Directive, HostListener, EventEmitter, Output } from "@angular/core";

@Directive({
    selector: "[scroll-directive]"
})
export class ScrollDirective {

    // <summary>
    // Event ouptut the current scroll percentage
    // </summary>
    @Output() onScroll = new EventEmitter<number>();

    // <summary>
    // Holds the current percent value
    // </summary>
    percentValue: number = 0;
    
    // <summary>
    // Event listener for scroll event on the specific ui element
    // </summary>
    @HostListener("scroll", ["$event"])
    onListenerTriggered(event: UIEvent): void {

        // Calculate the scroll percentage
        const percent = Math.round((event.srcElement.scrollTop / (event.srcElement.scrollHeight - event.srcElement.clientHeight)) * 100);

        // Compare the new with old and only raise the event if values change
        if(this.percentValue !== percent){
          
          // Update the percent value
          this.percentValue = percent;

          // Emit the event
          this.onScroll.emit(percent);
        }
    }
}

import {Component, VERSION} from '@angular/core'

@Component({
  selector: 'box',
  templateUrl: 'src/box.component.html'
})
export class BoxComponent {
  
  percent: number = 0;

   track(value: number): void {
      this.percent = value;
  }
}

<div>
  <h2>{{percent}}%</h2>
</div>

<div scroll-directive (onScroll)="track($event)" class="box">
    bla<br/>
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</div>