Additional Feature BA

ECMAScript No-Stage Proposal. Living Document. J. S. Choi, 2018-12.

This document is not yet intended to be officially proposed to TC39 yet; it merely shows a possible extension of the Core Proposal in the event that the Core Proposal is accepted.

An additional feature – bare awaited calls – would make async function calls terser. It adds another mode to bare style: if a bare-style pipeline step is preceded by a await, then instead of a mere function call, it is an awaited function call. value |> await object.asyncFunction is equivalent to await object.asyncFunction(value). This would be backwards compatible with the Core Proposal as well as all other additional features.

Additional Feature BA is formally specified in in the draft specification.

value
|> # + '!'
|> new User.Message(#)
|> await stream.write
|> console.log;

console.log(
  await stream.write(
    new User.Message(
      value + '!'
    )
  )
);

If a pipeline step starts with await, followed by a mere identifier, optionally with a chain of properties, and with no parentheses or brackets, then that identifier is interpreted to be a bare awaited function call.

That is: if a pipeline is of the form
topic |> await identifier
or topic |> await identifier0.identifier1
or topic |> await identifier0.identifier1.identifier2
or so forth,
then the pipeline is a bare async function call.

[Unix pipe]: https://en.wikipedia.org/wiki/Pipeline_(Unix [untangled flow]: ./goals.md#untangled-flow [Visual Basic’s select statement]: https://docs.microsoft.com/en-us/dotnet/visual-basic/language-reference/statements/select-case-statement [WebKit console variables]: https://webkit.org/blog/829/web-inspector-updates/ [WHATWG Fetch + CP]: ./core-real-examples.md#whatwg-fetch-standard [WHATWG Fetch Standard]: https://fetch.spec.whatwg.org/ [WHATWG Streams + CP + BP + PF + NP]: ./additional-feature-np.md#whatwg-streams-standard-core-proposal--additional-features-bppfmt [WHATWG Streams + CP + BP + PF]: ./additional-feature-pf.md#whatwg-streams-standard-core-proposal--additional-feature-bppf [WHATWG Streams Standard]: https://stream.spec.whatwg.org/ [WHATWG-stream piping]: https://streams.spec.whatwg.org/#pipe-chains [Wikipedia: term rewriting]: https://en.wikipedia.org/wiki/Term_rewriting [zero runtime cost]: ./goals.md#zero-runtime-cost