Fullstack-web

  Create an Observable using RxJS:   Import the Observable                                    import  {  Observable  }  from   'rxjs' ; The Observable execution deliver three types of values: "Next" - sends a value such as a Number, a String, an Object, etc. "Error - sends the Error or exception. "Complete" - does not send a value after the Complete                                             ngOnInit ():  void  {                    this . observable$  =  new   Observable ( subscriber   =>  {                      subscriber . next ( 1 );                      subscriber . next ( 2 );                      subscriber . next ( 3 );                      subscriber . complete ();  //Complete the subscribing here                      subscriber . next ( 4 );   // Value not send after complete                   });                    this . observable$ . subscribe ( value   =>  {                      console . log ( value );   

  What is RxJS? The full form of RxJS is  Reactive Extension for Javascript . As per the official website of RxJS - RxJS is a 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 by   Array#extras  (map, filter, reduce, every, etc) to allow handling asynchronous events as collections To manage the sequence of events RxJS combines the Observer pattern with the  Iterator pattern  and functional programming with collections   Observer Pattern: It is a software design pattern in which an object called Subject maintains a list of its dependents called Observers. It works well for applications that expect real-time updates. It is one to many patterns which are one Subject Many Observers. When the subject is updated it will automatically fire an event and notify the observers of the state changes and it carries some data