kefir.handle

Adapts the generic withHandler(handler) format to work more like the syntax observe(observer).

Installation

NPM

npm install kefir.handle

Usage

import handle from 'kefir.handle';

stream.withHandler(handle({
  value(emitter, value, event) { /* ...do stuff... */ },
  error(emitter, value, event) { /* ...do stuff... */ },
  end(emitter, value, event)   { /* ...do stuff... */ },
}));

A handler is an object with 3 optional methods:

• value - called when the source observable emits a value
• error - called when the source observable emits an error
• end - called when the source observable has ended

Each of these handlers are invoked with three arguments: an emitter, the value of the event, and an event object.

Please note, an undefined handler will automatically re-emit events of that type:

import Kefir from 'kefir';
import handle from 'kefir.handle';

var source = Kefir.sequentially(100, [0, 1, 2, 3]);
var result = source .withHandler(handler());

result.log();

> [sequentially.withHandler] <value> 1
> [sequentially.withHandler] <value> 2
> [sequentially.withHandler] <value> 3
> [sequentially.withHandler] <end>

source:  ---0---1---2---3X
result:  ---•---•---•---•X
            0   1   2   3

This is the opposite of the way that Kefir.withHandler() works. If you want to discard events, you can use the exported throwaway helper:

import handle, { throwaway } from 'kefir.handle';

stream.withHandler(handle({
  value: throwaway,
  error: throwaway,
  end:   throwaway,
}));

Converting the withHandler() example from the Kefir.js documentation.

import Kefir from 'kefir';
import handle from 'kefir.handle';

var source = Kefir.sequentially(100, [0, 1, 2, 3]);
var result = source.withHandler(handle({
    value(emitter, value) {
      for (var i = 0; i < value; i++) {
        emitter.emit(value);
      }
    },
    end(emitter) {
      emitter.emit('bye');
      emitter.end();
    },
  }));

result.log();

> [sequentially.withHandler] <value> 1
> [sequentially.withHandler] <value> 2
> [sequentially.withHandler] <value> 2
> [sequentially.withHandler] <value> 3
> [sequentially.withHandler] <value> 3
> [sequentially.withHandler] <value> 3
> [sequentially.withHandler] <value> bye
> [sequentially.withHandler] <end>

source:  ---0---1--- 2---  3 X
result:  -------•---••---••••X
                1   22   333bye