rxviz_groupby.js

const { interval, of, from } = Rx;
const { take, delay, map, switchMap, groupBy, mergeMap, toArray } = RxOperators;

const foo1 = {
	items: []
};
const foo2 = {
	items: [1,2,3]
};
const foo3 = {
	items: [1,2,2]
};
const foo4 = {
	items: [1,1,1,2,2,2,2]
};

const input = [foo1, foo2, foo3, foo4];

interval(1000)
.pipe(
  take(4),
  map(i => input[i]),
  map(obj => obj.items),
  switchMap( arr => from(arr)),
  groupBy(num => num),
//  mergeMap(group => group.pipe(toArray()))
)