Function: firstValueFrom()

firstValueFrom<T>(stream): Promise<T>

Defined in: converters/firstValueFrom.ts:24

Returns a promise that resolves with the first emitted value from a Stream.

This utility function bridges the gap between the stream's push-based system and JavaScript's standard promise-based asynchronous programming model. It's designed for scenarios where you only care about the very first value a stream produces, treating the stream like a single-value asynchronous source.

The function's behavior is as follows:

• If the stream emits a value, the promise resolves with that value.
• If the stream emits an error, the promise rejects with that error.
• If the stream completes without ever emitting a value, the promise rejects with an Error.

Once the promise is either resolved or rejected, the subscription to the stream is automatically terminated, preventing any further resource consumption. This makes it an efficient way to "query" a stream for a single result.

Type Parameters

T

T = any

The type of the value that the promise will resolve with.

Parameters

stream

Stream<T>

The source stream to listen to.

Returns

Promise<T>

A promise that resolves with the first value from the stream or rejects on error or completion without a value.