groupBy function

Is there an alternative to baconjs’s function groupBy also in kefir available? If not, would it be accepted as PR?

[mAAdhaTTah]

The use of Kefir.later means that the value is being emitted after the test ends. Either use Kefir.constant, which will emit the value immediately, or use toEmitInTime and tick to advance the clock & emit that value.

[niecore]

If someone is looking for the solution:

const T = require("transducers-js");
const Kefir = require("kefir");

const groupBy = (keyF, limitF) => src => {
    const streams = {};

    return src.transduce(T.comp(
        T.filter((x) => !streams[keyF(x)]),
        T.map(function(firstValue) {
            const key = keyF(firstValue);
            const similarValues = src.changes().filter(x => keyF(x) === key );
            const data  = Kefir.later(0, firstValue).concat(similarValues);

            const limited = limitF(data, firstValue).withHandler((emitter, event) => {

                if (event.type === 'end') {
                    delete streams[key];
                    emitter.end();
                } else {
                    emitter.emit(event.value);
                }
            });

            streams[key] = limited;
            return limited;
        })
))};