How to filter an array with RxJS operator

Question

Hello to every one i am new to RxJs and reactive programming i would like to filter an array like this:

let subscription = Rx.Observable.from([{id: 1}, {id: 2}, {id: 3}],[{id: 4}, {id: 5}, {id: 6}]);

if i have one array a i can do this:

let subscription = Rx.Observable.from([{id: 1}, {id: 2}, {id: 3}]);


subscription.filter(x => x.id === 1).subscribe(x => console.log(x));

But how i can to do with the second array?

Do you want to emit all the {id : n} object from your two arrays? — Axnyff
– Axnyff, Commented Jan 7, 2018 at 11:01

martin · Accepted Answer · 2018-01-07 11:43:30Z

4

If you know you'll always have array of arrays you can flatten the array and then run filter:

const o = Rx.Observable.of([{id: 1}, {id: 2}, {id: 3}],[{id: 1}, {id: 2}, {id: 3}])
  .concatMap(array => array) // flatten the array into single emissions
  .filter(x => x.id === 1)
  .subscribe(x => console.log(x));

I'm using .of that accepts multiple arguments. However it takes them as they are unlike the from method that iterates the array.

answered Jan 7, 2018 at 11:43

martin

97.4k26 gold badges205 silver badges237 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Axnyff · Accepted Answer · 2018-01-07 11:14:55Z

0

There are a couple of solutions. The easy way is just to create the right observable.

You could directly create the right observable by concatenating the array in your input of from:
```
let subscription = Rx.Observable.from([{id: 1}, {id: 3}].concat([{id: 1}]));
```
You could use Rx.Observable.of which directly takes as many arguments as value in the created Observable and use the spread operator:
```
let subscription = Rx.Observable.of(...[{id: 1}, {id: 3}].concat(...[{id: 1}]));
```

You could also merge two different observables:

let subscription = Rx.Observable.from([{id: 1}
                      .merge(Rx.Observable.from([{ id: 1}]);

There are possibly other solutions that could work like using an array of array and then flatMapping the array.

answered Jan 7, 2018 at 11:14

Axnyff

10.1k4 gold badges36 silver badges40 bronze badges

2 Comments

erevos13 Over a year ago

yes that very nice. But what about in case where i receive from an API and is an already mult array. ?

Axnyff Over a year ago

It's an array of arrays? If so, the flatMapping should work. subscription.flatMap(x => Rx.Observable.from(x))

Collectives™ on Stack Overflow

How to filter an array with RxJS operator

2 Answers 2

Comments

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related