Htykuut

Let's say I have an Observable stream created from an array like so:

const items: Items = [{},{},{},{},{},...];

const obs$ = from(items).pipe(

    mergeMap(items => {

        return this.getData(items);

    })

);

As this code stands, getData() will be called for each item in the array. What I want to do is divide the items array into N equal sized arrays, then have those arrays emitted instead. Then getData() will be called with the individual arrays rather than each item in the original items array.

Basically I need a variation of the toArray() operator but on only portions of the stream that I pre-define.

You need buffer operator which has several variations, which are: buffer, bufferCount, bufferTime, bufferToggle, bufferWhen. Buffer Official Documentation

For example in your case dividing array in 3 size arrays would be:

const items: Items = [{},{},{},{},{},...];

const obs$ = from(items).pipe(

    bufferCount(3),

    mergeMap(items => {

        return this.getData(items);

    })

);