operators in RxJS 6? ..... 13 4. RxJS — Observables ..... 15 Create Observable ..... 15 Subscribe Observable ..... 16 Execute Observable ..... 16 5. RxJS — Operators ..... 18 Working with Operators RxJS — Working with Subjects ..... 86 Create a subject ..... 86 What is the Difference between Observable and Subject? ..... 89 Behaviour Subject ..... 91 Replay Subject ..... 92 AsyncSubject .. library for composing asynchronous and event-based programs by using observable sequences. It provides one core type, the Observable, satellite types (Observer, Schedulers, Subjects) and operators inspired

implementation for TC39 Observable proposal ## What is RxJS? Push based primitive in JavaScript Domain specific language that sits on top of JS Ref implementation for TC39 Observable proposal ## What is primitive in JavaScript Domain specific language that sits on top of JS Ref implementation for TC39 Observable proposal ## What is RxJS? Only external dependency to Angular (2x) Push based primitive in JavaScript JavaScript Domain specific language that sits on top of JS Ref implementation for TC39 Observable proposal Easy to chain together complex interactions ## RxJS Authors ![Image](/uploads/documents/b/

of the abstract machine. Rather, conforming implementations are required to emulate (only) the observable behavior of the abstract machine as explained below. $ ^{4} $ (my emphasis) ## Characteristics Machine • Implementation • Parametrized • Non-deterministic • Implementations must emulate the observable behavior of the abstract machine ## Characteristics of the Abstract Machine ## • Implementation machine and generate an executable image (compiler, linker) - Implementations must emulate the observable behavior of the abstract machine ## • Parametrized ## • Non-deterministic ## Defining the Abstract

Pipes ..... 54 Creating custom pipe ..... 59 9. Angular 8 — Reactive Programming ..... 62 Observable ..... 62 Subscribing process ..... 63 Operations ..... 64 10. Angular 8 — Services and Dependency subscribes to an observable and returns the transmitted values. import { Observable, Observer } from 'rxjs'; export class TestComponent implements OnInit { timeChange = new Observable((observer: emitted from one source called Observable and the emitted data stream to be caught by other sources called Observer through a process called subscription. This Observable / Observer pattern or simple Observer

mutable. ## To the rescue ## I mmutability and Observable  ## Observable • Observable (by Ben Lesh, speaker from last JS Conf until someone subscribes to it. - Angular Uses RxJs Observable for subscription based processing of asynchronous operations. let observable = new Observable(observer => { const operation = fn((value ## • Observable input ☐ Component can only change if one of its input emits an event. ○ Component’s data can change without its input or parent or up change. ## AngularAsync Pipe and Observable • Subscribes

constructor(language: string, framework: string) { this.language = ko.observable(language); this.framework = ko.observable(framework); } } ko.applyBindings(new HelloViewModel("TypeScript" ： 1. // observable.ts 2. export class Observable { 3. // ... implementation left as an exercise for the reader ... 4. } 5. 6. // map.ts 7. import { Observable } from "./observable"; 8. Observable.prototype.map = function (f) { 9. // ... another exercise for the reader 10. } 它也可以很好地工作在TypeScript中，但编译器对 Observable.prototype.map 一无所知。你可以使用扩展模块来将它告诉编译器： 1. // observable.ts 2. export

. 59 iv Angular based navigation ..... 61 9. NativeScript — Events Handling ..... 64 Observable Class ..... 64 Event Listener ..... 64 Modifying BlankNgApp ..... 65 10. NativeScript event is fired. ## Observable Class It is a pre-defined class to handle events. It is defined below: const Observable = require("tns-core-modules/data/observable").Observable; In NativeScript NativeScript, almost every object derives from Observable class and so every object support events. ## Event Listener Let us understand how to create an object and add an event listener to the object in this chapter

Promise ## OBSERVABLE class Observable { func map(body: T -> U) -> Observable func flatMap(body: T -> Observable) -> Observable }

has no side effects: They don’t alter the state of the program, global variables, or produce any observable interactions with the outside world, such as writing to files or displaying output ## Pure Functions has no side effects: They don’t alter the state of the program, global variables, or produce any observable interactions with the outside world, such as writing to files or displaying output • Why is this has no side effects: They don’t alter the state of the program, global variables, or produce any observable interactions with the outside world, such as writing to files or displaying output • Why is this

Baz { var currentBar: Bar? val observable: Observable val foo = createBar().also { currentBar = it // Accessing property of Baz observable.registerCallback(it) // Passing context library. Examples include: — lazy properties: the value gets computed only upon first access; — observable properties: listeners get notified about changes to this property; — storing properties in a map which doesn't incur any thread-safety guarantees and the related overhead. ## Observable Delegates.observable() takes two arguments: the initial value and a handler for modifications. The handler