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withLatestFrom

withLatestFrom

rxjs.dev

Adds the second stream's latest value to the main stream's value.

Signature

withLatestFrom(other$: ObservableInput): OperatorFunction

Marble diagram

main:     --a---b---c---|
other:    ---1---2------|
result:   ------[b,1]-[c,2]-|

What it does

Emits only when the main stream ticks. It attaches the latest value of the "passive" other$ to the main value. If other$ hasn't emitted yet, the main value is ignored.

When to use

A click + the current filter state, a form submit + the current user, an event + config. When other$ is needed only as context, not as a trigger.

See also

combineLatest, sample, switchMap

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