Vector Programming and Reactive Javascript

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The Functional Part

Don’t describe how to process the data using a loop instead have your code state what you want to happen.

Use functional concepts to build nice observable streams:

  • Map: transform one collection into another.
  • Filter: filter one collection into a smaller collection.
  • Reduce: take a collection and reduce it into a single result (like inject in Ruby).
  • Zip: zip two collections into a single collection.

Reactive programming requires thinking functionaly.

Observables

  • Turn events into collections.
  • Allow you to handle errors in the collection.
  • Unsubscribe when the event is done.

Observable methods

  • merge: combine collections into a collection as each item arrives.
  • concatAll: combine collections into a new collection in the order in which they were created. Flatten async requests and resolve race conditions.
  • takeUntil: creates a single observable of a source collection and a stop collection. When event from stop collection occurs unsubscribe from source.
  • switchLatest: only use the latest collection. Throw out the rest.
  • distinctUntilChanged: filters out duplicate occurrences.

Example

(from https://github.com/Reactive-Extensions/RxJS)


/* Only get the value from each key up */
var keyups = Rx.Observable.fromEvent($input, 'keyup')
  .map(function (e) {
      return e.target.value;
  })
  .filter(function (text) {
      return text.length > 2;
  });

/* Now throttle/debounce the input for 500ms */
var throttled = keyups
  .throttle(500 /* ms */);

/* Now get only distinct values, so we eliminate the arrows and other control characters */
var distinct = throttled
  .distinctUntilChanged();
</pre>


Resources

- Reactive-Extensions for Javascript
- Learn Reactive Programming by jhusain
- Asynchronous JavaScript at Netflix
- Adding Even More Fun to Functional Programming With RXJS

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