Function annotate

Annotates values from source. Output values will be in the form { value: TIn, annotation: TAnnotation }. Where TIn is the type of the input, and TAnnotation is the return type of the annotator function.

Example calculating area from width & height:

const data = Rx.From.array(
 { w: 1, h: 3 }, { w: 1, h: 1 }, { w: 2, h: 2 }
);
const annotated = Rx.Ops.annotate(data, v => {
 return { area: v.w * v.h }
});
const data = await Rx.toArray(annotated);
// Data =  [ { value: { w:1, h:3 }, annotation: { area:3 } } ...]
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If you would rather annotate and have values merge with the input, use transform:

const data = Rx.From.array(
 { w: 1, h: 3 }, { w: 1, h: 1 }, { w: 2, h: 2 }
);
const withArea = Rx.Ops.transform(data, v => {
 return { ...v, area: v.w * v.h }
});
const data = await Rx.toArray(withArea);
// Data =  [ { w:1, h:3, area:3 }, ...]
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