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[preset-env] ios8 Computed property names wont transfer in strict mode #10503

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qiyunbao opened this issue Sep 27, 2019 · 2 comments

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@qiyunbao
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commented Sep 27, 2019

Bug Report

Current Behavior
when set env target to ios8, @babel/preset-env won‘t transform Computed property names syntax, which in ios8 is not fully support in strict mode.

Input Code

(function () {
   "use strict";
    var C = {
       y: '12',
       m: '13',
     };
   var result = {
      [C.y]: 'abc',
      [C.m]: 'cde',
    };
    console.log(result);
 });

Expected behavior/code
If the target is set to ios8, babel-env should transfer the code to es5, but now it will keep the syntax and ios8 will throw an Error like this SyntaxError: Attempted to redefine proerty '12'

In caniuse.com, it says ios 8 support Computed property names Syntax, but the true is, it has some bug in strict mode. the code above will throw error, If you useing only one [C.y] or only [C.m] it is ok, but together it will throw the error,in none strict mode, is is ok too. I believe it is some werid bug in ios 8 webview

Babel Configuration (.babelrc, package.json, cli command)

// preset-env's config
{
  "targets": { "ios": 8 }
}

Environment

  • Babel version(s): 7.4.3
  • Node/npm version: Node 10/npm 6
  • OS: ios8.4
  • How you are using Babel: loader

Possible Solution

this Syntax should be transfer to es5 in ios8 target

Additional context/Screenshots
Add any other context about the problem here. If applicable, add screenshots to help explain.

@babel-bot

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commented Sep 27, 2019

Hey @qiyunbao! 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 community that typically always has someone willing to help. You can sign-up here for an invite."

@JLHwung

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commented Sep 27, 2019

The browser feature data in preset-env is aligned to caniuse. In this data every browser will have a range of versions in which the feature is natively supported. We would not mark any specific version as unsupported if the implementation is faulty under some edge cases.

Note that you can use include option of preset-env to enable @babel/plugin-transform-computed-properties.

// preset-env's config
{
  "targets": { "ios": 8 },
  "include": ["@babel/plugin-transform-computed-properties"]
}
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