NG Observables - suniladhya/Advantage GitHub Wiki

[1] Observable is a wrapper around a data source, i.e. some stream of data. They are used for asynchronous data.

Promise:

Observables Promises
Emit multiple values over a period of time. Emit a single value at a time.
Are lazy: they’re not executed until we subscribe to them using the subscribe() method. Are not lazy: execute immediately after creation.
Have subscriptions that are cancellable using the unsubscribe() method, which stops the listener from receiving further values. Are not cancellable.
Provide the map for forEach, filter, reduce, retry, and retryWhen operators. Don’t provide any operations.
Deliver errors to the subscribers. Push errors to the child promises. 
 <e-series-collection>
      <e-series [dataSource]='chartData' type='Spline' xName='year' yName='sales'> </e-series>
  </e-series-collection>`
 
export class AppComponent  {
 
  public chartData: Data[];
  constructor(private dataService: DataService) { 
 
  }
  new Promise((resolve, reject) => 
                   {
                    resolve(this.dataService.getData())
                   }
              ).then((value : Data[]) => 
                    this.chartData = value
              ).catch((err) => 
                     this.chartData = null
              );   
}
this.Obs = new Observable((observer) => {
             observer.next(this.dataService.getData(true));
             setInterval(() => {
               observer.next(this.dataService.getData(false));
              }, 1000)
          });
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