Observables Workshop

This is a dojo on the Zen Observable library: https://github.com/zenparsing/zen-observable

It has been adapted from the exercises kindly set up by https://github.com/araqnid (many thanks!)

Introduction

• Run npm install
• To execute tests, run npm test
• Work through each of the exercises, for each test:
  • Unignore the test (by changing xit to it)
  • Make the test pass

Exercises

Standalone usage

• Create an observable to emit the rainbow colours, and subscribe to it to print them out
  • Passing an object to subscription
  • Passing just functions to subscription
• Observable.of() emits a sequence of values
• Observable.forEach() as an alternative

Timing and observables

• Write an Observable to make a delay
• Write an Observable to output values at a fixed rate

Using Observables instead of callbacks

• Given a simple callback-based API (e.g. nanoajax), wrap it up as an Observable
• The same with an API that takes onSuccess and onError callbacks

Composing Observables

• Wrap an Observable in another Observable to transform its output
  • Simple transforms are simple, subscription is container’s unsubscribe
• Use the .map method
• Use the .filter method
• Write an Observable to emit the values of other Observables in turn
  • Use the .concat method
• Write an Observable to propagate values from an underlying Observable at a fixed rate (auto-refresh)
• Zen-observable provides some combining functions: merge, combineLatest, zip
  • Should have all the pieces (delay, concat) now to easily demonstrate what these do