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Add pipeline operator "loose" mode #10135

jhpratt opened this issue Jun 26, 2019 · 1 comment


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commented Jun 26, 2019

Feature Request

Right now, the pipeline operator (|>) always creates a temporary variable to store a reference. Per the spec, this is correct, as evaluation order is different. What I'm asking is for that to not be the case (given a "loose" option). A "loose" option is present for multiple other proposals, so it's not without precedent.

Here's an example from the pipeline proposal.

|> # - 3
|> -#
|> # * 2
|> Math.max(#, 0)
|> console.log;

Current transformation:

var _ref, _ref2, _ref3, _ref4, _input;

_ref = (
  _ref2 = (
    _ref3 = (
      _ref4 = (
        _input = input,
        _input - 3
    _ref3 * 2
  Math.max(_ref2, 0)

Proposed transformation:

    -(input - 3) * 2,

To avoid wasted effort, it's probably best to wait until TC39 settles on a specific syntax proposal before implementing, as there are many, and Babel will support 3 (minimal, smart, and F#) as of Babel 7.5.


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commented Jun 26, 2019

Hey @jhpratt! We really appreciate you taking the time to report an issue. The collaborators
on this project attempt to help as many people as possible, but we're a limited number of volunteers,
so it's possible this won't be addressed swiftly.

If you need any help, or just have general Babel or JavaScript questions, we have a vibrant Slack
that typically always has someone willing to help. You can sign-up here
for an invite.

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