WARNING: This library has been superseded by the Karet Lift library.

The default export of this library

import K from "kefir.combines"

is a special purpose Kefir observable combinator designed for combining properties for a sink that accepts both observables and constant values such as VDOM extended to accept observables.

Unlike typical observable combinators, when K is invoked with only constants (no observables), then the result is computed immediately and returned as a plain value. This optimization eliminates redundant observables.

The basic semantics of K can be described as

K(x1, ..., xN, fn) === combine([x1, ..., xN], fn).skipDuplicates(identical)

where combine and skipDuplicates come from Kefir and identical from Ramda. Duplicates are skipped, because that can reduce unnecessary updates. Ramda's identical provides a semantics of equality that works well within the context of embedding properties to VDOM.

Unlike with combine, any argument of K is allowed to be

• a constant,
• an observable (including the combiner function), or
• an array or object containing observables.

In other words, K also provides functionality similar to combineTemplate.

Note: K is carefully optimized for space—if you write equivalent combinations using Kefir's own operators, they will likely take more memory.