Additional Feature BC

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 constructor calls – would make constructor calls terser. It adds a mode to bare style: if a bare-style pipeline step is preceded by a new, then instead of a function call, it is a constructor call. value |> object.Constructor is equivalent to object.Constructor(value). This is backwards compatible with the Core Proposal as well as all other additional features.

Additional Feature BC 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 new, 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 constructor.

That is: if a pipeline is of the form
topic |> new identifier
or topic |> new identifier0.identifier1
or topic |> new identifier0.identifier1.identifier2
or so forth,
then the pipeline is a bare constructor 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