callbag-tap-up

Callbag operator which performs a side effect for every upwards emission (from sink to source), but other than that it acts as noop.

Example

``js
import forEach from 'callbag-for-each'
import fromIter from 'callbag-from-iter'
import pipe from 'callbag-pipe'
import take from 'callbag-take'
import tapUp from 'callbag-tap-up'

pipe(
fromIter([10, 20, 30, 40, 50]),
tapUp(
data => console.log(data), // always undefined in this example (forEach doesn't send anything up)
err => console.log(err),
() => console.log('unsubscribed'),
),
take(2),
forEach(values => {
console.log(values) // 10, 20
}),
)
``