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Function: join()

join<L, R, Out>(left, right, config): Stream<Out[]>

Defined in: packages/core/src/graph/transforms.ts:47

Relational join of two array streams.

const joined = join(enriched, classified, { on: (e, c) => e.id === c.id, emit: (e, c) => ({ ...e, category: c.category }), }); // Stream<{ id, ..., category }[]>

Cross-joins the two input arrays, applies on as the match predicate, and emits one row of output per matching (l, r) pair. l / r in the callbacks are typed by the input streams — hover either in an IDE and the exact row shape appears. Output element type is inferred from emit.

Why arrays: a single-row stream of L joined with a single-row stream of R is equivalent to merge({left, right}).pipe(...) and wouldn't earn the name "join". The useful case is "take an array of enriched rows and an array of classified rows, pair them by id" — that's what this signature supports.

Type Parameters​

L​

L

R​

R

Out​

Out

Parameters​

left​

Stream<readonly L[]>

Stream<readonly R[]>

config​

emit​

(l, r) => Out

on​

(l, r) => boolean

Returns​

Stream<Out[]>