They do the same. `emit()` is the current version, `next()` is deprecated.

See also https://github.com/angular/angular/blob/b5b6ece65a96f5b8f134ad4899b56bf84afe3ba0/modules/angular2/src/facade/async.dart#L49

In the latest version(Ng9), the source code of `event_emitter.ts` goes as following:

```
export class EventEmitter&lt;T extends any&gt; extends Subject&lt;T&gt; {
  /**
   * Emits an event containing a given value.
   * @param value The value to emit.
   */
  emit(value?: T) { super.next(value); }
}

```

`EventEmitter` extends from parent class `Subject`. And `emit` method call `super.next()` as you may expected. 

How can I copy more than a single file into remote nodes by Ansible in a task?

I&#39;ve tried to duplicate the copy module line in my task to define files but it only copies the first file.

Copy multiple files with Ansible

As I write webpack.config.js like this 

    module.exports = {
      entry: &#39;./index.jsx&#39;,
      output: {
        filename: &#39;bundle.js&#39;
      },
      module: {
        loaders: [{
          test: /\.jsx?$/,
          exclude: /node_modules/,
          loader: &#39;babel&#39;,
          query: {
            presets: [&#39;es2015&#39;, &#39;react&#39;]
          }
        }]
      }
    };

And in `index.jsx` I import a `react` module `App`

    import React from &#39;react&#39;;
    import { render } from &#39;react-dom&#39;;
    
    import App from &#39;./containers/App&#39;;
    
    let rootElement = document.getElementById(&#39;box&#39;)
    render(
      &lt;App /&gt;,
      rootElement
    )

I find if I named module app in `App.jsx`, then webpack will say in `index.jsx` can&#39;t find module `App`, but if I named named module app in `App.js`, it will find this module and work well.

So, I&#39;m confuse about it. In my `webpack.config.js`, I have writed `test: /\.jsx?$/` to check file, but why named `*.jsx` can&#39;t be found?

[![enter image description here][1]][1]


  [1]: http://i.stack.imgur.com/cRtyD.png

webpack can&#39;t find module if file named jsx

What is the difference between `EventEmitter.emit()` and `EventEmitter.next()`? Both dispatching the event to the subscribed listeners.

&lt;!-- language: lang-js --&gt;

    export class MyService {
      @Output() someEvent$: EventEmitter&lt;any&gt; = new EventEmitter();
    
      someFunc() {
       this.someEvent$.emit({myObj: true});
    
       this.someEvent$.next({myObj: true});
      }
    }

The [documenation for the EventEmitter](https://angular.io/docs/ts/latest/api/core/EventEmitter-class.html) is not so helpful at the moment.

Difference between EventEmitter.next() and EventEmitter.emit() in Angular 2

What is the difference between <code>EventEmitter.emit()</code> and <code>EventEmitter.next()</code>? Both dispatching the event to the subscribed listeners.

<pre><code class="hljs language-typescript">export class MyService {
 @Output() someEvent$: EventEmitter&#x3C;any> = new EventEmitter();

 someFunc() {
 this.someEvent$.emit({myObj: true});

 this.someEvent$.next({myObj: true});
 }
}
</code></pre>
The <a href="https://angular.io/docs/ts/latest/api/core/EventEmitter-class.html" target="_blank" rel="noopener noreferrer">documenation for the EventEmitter</a> is not so helpful at the moment.

If I want function x to happen every time a component loads, whether its the first time, I navigate to a different site and navigate back or it&#39;s the fifth time the component has loaded.

What should I put function x in? The component constructor or OnInit?

Angular 2 Component Constructor Vs OnInit

I am having trouble finding a good autocomplete component for Angular2. Just anything that I can pass a list of key-label objects to and have a nice autocomplete on an `input` field.

Kendo does not support Angular 2 yet and that it what we mostly use internally.  It doesn&#39;t appear that Angular Material supports Angular 2 yet either.

Can anyone please point me in the right direction or let me know what they are using?

This is what I built so far.  It&#39;s pretty bad and I&#39;d like to find something that looks nice.

&lt;!-- language: lang-ts --&gt;

    import {Component, EventEmitter, Input, Output} from &#39;angular2/core&#39;;
    import {Control} from &#39;angular2/common&#39;;
    import {Observable} from &#39;rxjs/Observable&#39;;
    import {SimpleKeyValue} from &#39;../models/simple-key-value&#39;
    import &#39;rxjs/add/operator/map&#39;;
    import &#39;rxjs/add/operator/debounceTime&#39;;
    import &#39;rxjs/add/operator/distinctUntilChanged&#39;;

    @Component({
    selector: &#39;general-typeahead&#39;,
    template: ` &lt;div&gt;
                &lt;div class=&quot;input-group&quot;&gt;
                &lt;input type=&quot;text&quot; [ngFormControl] = &quot;term&quot; class=&quot;form-control&quot; placeholder={{placeHolder}} &gt;
                &lt;/div&gt;
                &lt;ul&gt;
                    &lt;li class=&quot;item&quot; *ngFor=&quot;#item of matchingItems&quot; (click)=&quot;selectItem(item)&quot;&gt;
                        {{item.value}}
                    &lt;/li&gt;
                &lt;/ul&gt;              
    &lt;/div&gt;`
    })

    export class GeneralTypeahead {
  
      matchingItems: Array&lt;SimpleKeyValue&gt;;
      term = new Control();

      @Input() allItems: Array&lt;SimpleKeyValue&gt;;
      @Input() placeHolder: string;
      @Output() onSelectItem = new EventEmitter&lt;SimpleKeyValue&gt;();

      constructor() {
        this.term.valueChanges
            .distinctUntilChanged()
            .debounceTime(200)
            .subscribe((term : string) =&gt; this.matchingItems = this.allItems.filter(sl =&gt; sl.value.toLowerCase().indexOf(term.toLowerCase()) &gt; -1));
      }

      selectItem(sl: SimpleKeyValue) {
        this.onSelectItem.emit(sl);
      }
    }

Implementing autocomplete

Let&#39;s say I have an Angular2 Component

    //home.component.ts

    import { Component } from &#39;angular2/core&#39;;

    @Component({
        selector: &quot;home&quot;,
        templateUrl: &quot;app/components/templates/home.component.html&quot;,
        styleUrls: [&quot;app/components/styles/home.component.css&quot;]
    })
    export class HomeComponent {
        public width: Number;
        public height: Number;
    } 

The template html file for this component

    //home.component.html
    
    &lt;div class=&quot;home-component&quot;&gt;Some stuff in this div&lt;/div&gt;

And finally the css file for this component
    
    //home.component.css

    .home-component{
        background-color: red;
        width: 50px;
        height: 50px;
    }

As you can see there are 2 properties in the class, `width` and `height`. I would like the css styles for width and height to match the values of the width and height properties and when the properties update, the width and height of the div update. What is the proper way to accomplish this?

Dynamically updating css in Angular 2

I have a ListComponent.  When an item is clicked in ListComponent, the details of that item should be shown in DetailComponent.  Both are on the screen at the same time, so there&#39;s no routing involved.

How do I tell DetailComponent what item in ListComponent was clicked?

I&#39;ve considered emitting an event up to the parent (AppComponent), and have the parent set the selectedItem.id on DetailComponent with an @Input.  Or I could use a shared service with observable subscriptions.

***
**EDIT:** Setting the selected item via event + @Input doesn&#39;t trigger the DetailComponent, though, in case I were to need to execute additional code.  So I&#39;m not sure this is an acceptable solution.
***

But both of these methods seem far more complex than the Angular 1 way of doing things which was either through $rootScope.$broadcast or $scope.$parent.$broadcast.

With everything in Angular 2 being a component, I&#39;m surprised there&#39;s not more information out there about component communication.

Is there another/more straightforward way to accomplish this?  

Angular 2 Sibling Component Communication

What is viewProviders in the below code? And how it differs from providers?

&lt;!-- language: lang-ts --&gt;

    class Greeter {
       greet(name:string) {
         return &#39;Hello &#39; + name + &#39;!&#39;;
       }
    }    
    @Component({
      selector: &#39;greet&#39;,
      viewProviders: [
        Greeter
      ],
      template: `&lt;needs-greeter&gt;&lt;/needs-greeter&gt;`    
    })
    class HelloWorld {
    }
    

What are viewproviders in Angular? And what is the difference b/w providers vs viewproviders?

I&#39;ve read questions like [Access EventEmitter Service inside of CustomHttp](https://stackoverflow.com/questions/36059564/access-eventemitter-service-inside-of-customhttp) 
where the user uses EventEmitter in his service, but he was suggested in this [comment](https://stackoverflow.com/questions/36059564/access-eventemitter-service-inside-of-customhttp#comment59766410_36059564) 
not to use it and to use instead Observables directly in his services. 

I also read this 
[question](https://stackoverflow.com/questions/36014395/angular-2-two-way-communication-between-components/36014451#36014451) 
where the solution suggests to pass the EventEmitter to the child and subscribe to it.

My question then is: Should I, or should I not subscribe manually to an EventEmitter? How should I use it?

What is the proper use of an EventEmitter?

I&#39;ve read that injecting when bootstrapping should have all children share the same instance, but my main and header components (main app includes header component and router-outlet) are each getting a separate instance of my services.  

I have a FacebookService which I use to make calls to the facebook javascript api and a UserService that uses the FacebookService.  Here&#39;s my bootstrap:

    bootstrap(MainAppComponent, [ROUTER_PROVIDERS, UserService, FacebookService]);

From my logging it looks like the bootstrap call finishes, then I see the FacebookService then UserService being created before the code in each of the constructors runs, the MainAppComponent, the HeaderComponent and the DefaultComponent:

[![enter image description here][1]][1]



  [1]: http://i.stack.imgur.com/6q6tG.png

How do I create a singleton service in Angular 2?

By using Http, we call a method that does a network call and returns an http observable:

&lt;!-- language-all: lang-js --&gt;

    getCustomer() {
        return this.http.get(&#39;/someUrl&#39;).map(res =&gt; res.json());
    }

If we take this observable and add multiple subscribers to it:

    let network$ = getCustomer();

    let subscriber1 = network$.subscribe(...);
    let subscriber2 = network$.subscribe(...);

What we want to do, is ensure that this does not cause multiple network requests.

This might seem like an unusual scenario, but its actually quite common: for example if the caller subscribes to the observable to display an error message, and passes it to the template using the async pipe, we already have two subscribers.

What is the correct way of doing that in RxJs 5? 

Namely, this seems to work fine:

    getCustomer() {
        return this.http.get(&#39;/someUrl&#39;).map(res =&gt; res.json()).share();
    }

But is this the idiomatic way of doing this in RxJs 5, or should we do something else instead? 

*Note : As per Angular 5 new `HttpClient`, the `.map(res =&gt; res.json())` part in all examples is now useless, as JSON result is now assumed by default.*

What is the correct way to share the result of an Angular Http network call in RxJs 5?

I have a Component and a Service:

Component:
&lt;!-- begin snippet: js hide: false console: true --&gt;

&lt;!-- language: lang-js --&gt;

    export class WebUserProfileViewComponent {
        persons: Person [];
        personId: number;
        constructor( params: RouteParams, private personService: PersonService) {
              
            
               this.personId = params.get(&#39;id&#39;);
               this.persons =  this. personService.getPersons();
               console.log(this.personId);  
            }
    }

&lt;!-- end snippet --&gt;

Service: 

&lt;!-- begin snippet: js hide: false console: true --&gt;

&lt;!-- language: lang-js --&gt;

    @Injectable()
    export class PersonService {
          getPersons(){
            var persons: Person[] = [
                {id: 1, firstName:&#39;Hans&#39;, lastName:&#39;Mustermann&#39;, email: &#39;mustermann@test.com&#39;, company:&#39;Test&#39;, country:&#39;DE&#39;},
                {id: 2, firstName:&#39;Muster&#39;, lastName:&#39;Mustermann&#39;, email: &#39;mustermann@test.com&#39;, company:&#39;test&#39;, country:&#39;DE&#39;},
                {id:3, firstName:&#39;Thomas&#39;, lastName:&#39;Mustermann&#39;, email: &#39;mustermannt@tesrt.com&#39;, company:&#39;test&#39;, country:&#39;DE&#39;}
            ];
              
            return persons;
          }
    }

&lt;!-- end snippet --&gt;

I want to get the Person item with the ID (&#39;personID&#39;). The personID I get from `Routeparams`. For that I need the foreach loop? But I haven&#39;t found a solution for this.

Angular 2 TypeScript how to find element in Array

In my Angular 2 component I have an Observable array

&lt;!-- language: lang-ts --&gt;

    list$: Observable&lt;any[]&gt;;

In my Template I have

&lt;!-- language: lang-html --&gt;

    &lt;div *ngIf=&quot;list$.length==0&quot;&gt;No records found.&lt;/div&gt;
    
    &lt;div *ngIf=&quot;list$.length&gt;0&quot;&gt;
        &lt;ul&gt;
            &lt;li *ngFor=&quot;let item of list$ | async&quot;&gt;item.name&lt;/li&gt;
        &lt;/ul&gt;
    &lt;/div&gt;

But list$.length doesn&#39;t work with in case of Observable array.


**Update:**

It seems that **(list$ | async)?.length** gives us the length but the below code still doesn&#39;t work:

&lt;!-- language: lang-html --&gt;

    &lt;div&gt;
        Length: {{(list$ | async)?.length}}
        &lt;div *ngIf=&quot;(list$ | async)?.length&gt;0&quot;&gt;
            &lt;ul&gt;
                &lt;li *ngFor=&quot;let item of (list$ | async)&quot;&gt;
                    {{item.firstName}}
                &lt;/li&gt;
            &lt;/ul&gt;
        &lt;/div&gt;
    &lt;/div&gt;

 Can anyone please guide how do I check length of Observable array.


Content Type	Original Author	Original Content on Stackoverflow
Question	Holger Stitz	View Question on Stackoverflow
Solution 1 - Angular	Günter Zöchbauer	View Answer on Stackoverflow
Solution 2 - Angular	Chris Bao	View Answer on Stackoverflow

Difference between EventEmitter.next() and EventEmitter.emit() in Angular 2

Angular Problem Overview

Angular Solutions

Solution 1 - Angular

Solution 2 - Angular

webpack can't find module if file named jsx

Copy multiple files with Ansible

Attributions