Can I observe additions to an array with rx.js?

Question

fromArray Rx wiki on github

coffee> rext = require \'rx\'                                                 
coffee> arr = [1..5]                                 


        

Answer 1

I found Rx.Observable.ofObjectChanges(obj) to work just as I expected.

From the documentation page:

Creates an Observable sequence from changes to an object using Object.observe.

Hope it helps.

Answer 2

How about this:

var subject = new Rx.Subject();
//scan example building an array over time
var example = subject.scan((acc, curr) => { 
    return acc.concat(curr);
}
,[]);

//log accumulated values
var subscribe = example.subscribe(val => 
    console.log('Accumulated array:', val)
);

//next values into subject
subject.next(['Joe']);
subject.next(['Jim']);

Answer 3

Observable.fromArray creates an Observable that immediately fires events for each array items, when you add a Subscriber. So, it won't be "watching" the changes to that array.

If you need a "pushable collection", the Bus class in Bacon.js might be what you're looking for. For RxJs there's my little MessageQueue class that has a similar functionality.

Answer 4

In RxJS what you are looking for is called a Subject. You can push data into it and stream it from there.

• Subject getting started guide
• Subject API docs.

Example:

var array = [];
var arraySubject = new Rx.Subject();

var pushToArray = function (item) {
  array.push(item);
  arraySubject.next(item);
}

// Subscribe to the subject to react to changes
arraySubject.subscribe((item) => console.log(item));