Callbag which creates a source from a given factory when sink subscribes.
import defer from 'callbag-defer'
import forEach from 'callbag-for-each'
import fromEvent from 'callbag-from-event'
import interval from 'callbag-interval'
import pipe from 'callbag-pipe'
pipe(
defer(() =>
Math.random() > 0.5 ? fromEvent(document, 'click') : interval(1000),
),
forEach(value => {
// value being either click event or a number
}),
)