1 introduction

• Push numbers
  • Hints
• Add a delay
  • Hints
• Unsubscribe
  • Hints
• Try timer
  • Hints

Table of contents generated with markdown-toc

Push numbers

• Open apps/playground/src/index.ts
• Create an observable
• Subscribe to the observable
• Push the numbers 1, 2, 3, 4
• Then complete
• Check the output
• Try pushing a value after complete
• Try throwing an error with the text something went wrong
• run npm run start:playground to start the app

Hints

import { Observable } from 'rxjs';

// Create observable
const helloWorld$ = new Observable(
  function subscribe(observer) {
    observer.next('Hello');
    observer.next('World');
    observer.complete();
  }
);

// Subscribe to an observable
helloWorld$.subscribe({
  next(x) {console.log(x);},
  error(err) {console.error(err);},
  complete() {console.log('done');}
});

Add a delay

• Push a value in a 1 second interval

Hints

// do something every second
setInterval(() => console.log('every second'), 1000);

Unsubscribe

• Clear the interval when unsubscribe is called
• Don't forget to wait some seconds before you unsubscribe

Hints

// do something every second
const interval = setInterval(() => console.log('every second'), 1000);

// stop interval
clearInterval(interval);

// wait 5 seconds before doing something
setTimeout(() => {
  console.log('after 5 seconds');
}, 5000);

Try timer

• Push a value every 2 seconds
• Wait 5 seconds before pushing the first value
• Check the output

Hints

import { timer } from 'rxjs';

const dueTime = 1000;
const period = 1000;

const observable$ = timer(dueTime, period);